…ass()` (#9769)

Context: xamarin/monodroid@ed984a3
Context: dotnet/java-interop#23

Update `JNIEnv.FindClass()` to use `JniEnvironment.Types.FindClass()`.

This avoids the problem of `JNIEnvInit.mid_Class_forName` being
`null` in a NativeAOT context:

	E AndroidRuntime: Process: net.dot.hellonativeaot, PID: 30744
	E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.TypeInitializationException: TypeInitialization_Type_NoTypeAvailable
	E AndroidRuntime:  ---> System.ArgumentNullException: ArgumentNull_Generic Arg_ParamName_Name, method
	E AndroidRuntime:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference, JniMethodInfo, JniArgumentValue*) + 0x1c8
	E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xb4
	E AndroidRuntime:    at Java.Lang.Class..cctor() + 0x7c
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0xb4
	E AndroidRuntime:    Exception_EndOfInnerExceptionStack
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0x160
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.CheckStaticClassConstructionReturnNonGCStaticBase(StaticClassConstructionContext*, IntPtr) + 0x14
	E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xc0
	E AndroidRuntime:    at Android.App.Application.get_Context() + 0x50
	E AndroidRuntime:    at Microsoft.Maui.Hosting.EssentialsExtensions.<>c.<UseEssentials>b__0_0(ILifecycleBuilder life) + 0x18
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventService..ctor(IEnumerable`1) + 0x94
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.MauiAppHostBuilderExtensions.<>c.<ConfigureLifecycleEvents>b__0_0(IServiceProvider sp) + 0x3c
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite, RuntimeResolverContext) + 0x68
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(ServiceIdentifier serviceIdentifier) + 0x180
	E AndroidRuntime:    at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey, Func`2) + 0x11c
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier, ServiceProviderEngineScope) + 0x44
	E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
	E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider) + 0x3c
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.<GetLifecycleEventDelegates>d__3`1.MoveNext() + 0x38
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.InvokeLifecycleEvents[TDelegate](IServiceProvider, Action`1) + 0x68
	E AndroidRuntime:    at Microsoft.Maui.MauiApplication.OnCreate() + 0xb0
	E AndroidRuntime:    at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) + 0xb0
	E AndroidRuntime: at my.MainApplication.n_onCreate(Native Method)
	E AndroidRuntime: at my.MainApplication.onCreate(MainApplication.java:24)
	E AndroidRuntime: at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1386)
	E AndroidRuntime: at android.app.ActivityThread.handleBindApplication(ActivityThread.java:7398)
	E AndroidRuntime: at android.app.ActivityThread.-$$Nest$mhandleBindApplication(Unknown Source:0)
	E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2379)
	E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:107)
	E AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:232)
	E AndroidRuntime: at android.os.Looper.loop(Looper.java:317)
	E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:8592)
	E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
	E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
	E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)

This also allows us to remove these fields that are now unused:

  * `JnienvInitializeArgs.Class_forName`
  * `JNIEnv.BinaryName()`

TODO?  While `JNIEnv.FindClass()` was using [`Class.forName()`][0],
`JniEnvironment.Types.FindClass()` uses [`ClassLoader.loadClass()`][1].
`JNIEnv.FindClass()` originally used `ClassLoader.loadClass()`, but
was changed to use `Class.forName()` in xamarin/monodroid@ed984a3a as
part of supporting the Xamarin.Android Designer.

Updating `JNIEnv.FindClass()` to use `JniEnvironment.Types.FindClass()`
effectively reverts that original change.  This is "fine" for now --
the Xamarin.Android Designer is no longer supported -- but in the
future we may want to update `JniEnvironment.Types.FindClass()` to
use `Class.forName()`; see dotnet/java-interop#23.

[0]: https://developer.android.com/reference/java/lang/Class#forName(java.lang.String)
[1]: https://developer.android.com/reference/java/lang/ClassLoader#loadClass(java.lang.String)

Fixes: #23

Context: dotnet/android@aba2726
Context: b4d44e4
Context: xamarin/monodroid@ed984a3
Context: dotnet/android#7616

Commit b4d44e4 noted:

> Android is..."special", in that not all threads get the same
> ClassLoader behavior. Specifically, *managed* threads --
> System.Threading.Thread instances -- get a different ClassLoader than
> the main/UI thread on Android. (Untested, but the ClassLoader *may*
> behave sanely if you use a java.lang.Thread instance instead. But who
> wants to use java.lang.Thread instances...?)

dotnet/android#7616 provided additional context: `JNIEnv::FindClass()`
behavior *is* tied to the thread that calls it, and one of the knock-on
effects is that `Java.Lang.JavaSystem.LoadLibrary("MyLib")` doesn't
work properly when invoked from a new `System.Threading.Thread` thread.

Which brings us to xamarin/mondroid@ed984a3a, which updated then
Xamarin.Android to use [`java.lang.Class.forName(String)`][0] instead
of [`ClassLoader.loadClass(String)`][1] because the "real" JDK cannot
use `ClassLoader.loadClass(String)` to load array types:

	Class c1 = Class.forName("[Ljava.lang.String;");    // works
	Class c2 = ClassLoader.getSystemClassLoader()
	    .loadClass("[Ljava.lang.String;");              // throws java.lang.ClassNotFoundException

	Class c3 = Class.forName("[I");                     // works; array of int
	Class c4 = ClassLoader.getSystemClassLoader()
	    .loadClass("[I");                               // throws java.lang.ClassNotFoundException

Using `ClassLoader.loadClass(String)` to load array types works on
Android, presumably as an undocumented implementation detail, but as
xamarin/monodroid@ed984a3a was trying to get things working within
the (now dead) Android Designer -- which ran using a Desktop JDK --
Android-specific extensions were not available.

Update `JniEnvironment.Types` to use `Class.forName(String)` instead
of `ClassLoader.loadClass(String)` to load Java classes, as a fallback
for when `JNIEnv::FindClass()` fails to find the class.

[0]: https://developer.android.com/reference/java/lang/Class#forName(java.lang.String)
[1]: https://developer.android.com/reference/java/lang/ClassLoader#loadClass(java.lang.String)

…#1326)

Fixes: #23

Context: dotnet/android@aba2726
Context: b4d44e4
Context: xamarin/monodroid@ed984a3
Context: dotnet/android#7616

Commit b4d44e4 noted:

> Android is..."special", in that not all threads get the same
> ClassLoader behavior. Specifically, *managed* threads --
> System.Threading.Thread instances -- get a different ClassLoader than
> the main/UI thread on Android. (Untested, but the ClassLoader *may*
> behave sanely if you use a java.lang.Thread instance instead. But who
> wants to use java.lang.Thread instances...?)

dotnet/android#7616 provided additional context: `JNIEnv::FindClass()`
behavior *is* tied to the thread that calls it, and one of the knock-on
effects is that `Java.Lang.JavaSystem.LoadLibrary("MyLib")` doesn't
work properly when invoked from a new `System.Threading.Thread` thread.
(This is still the case, by the way.)

Which brings us to xamarin/mondroid@ed984a3a, which updated then
Xamarin.Android to use
[`Class.forName(String name, boolean initialize, ClassLoader loader)`][0]
instead of [`ClassLoader.loadClass(String)`][1], because the "real"
JDK cannot use `ClassLoader.loadClass(String)` to load array types:

	Class c1 = Class.forName("[Ljava.lang.String;");    // works
	Class c2 = ClassLoader.getSystemClassLoader()
	    .loadClass("[Ljava.lang.String;");              // throws java.lang.ClassNotFoundException

	Class c3 = Class.forName("[I");                     // works; array of int
	Class c4 = ClassLoader.getSystemClassLoader()
	    .loadClass("[I");                               // throws java.lang.ClassNotFoundException

Using `ClassLoader.loadClass(String)` to load array types works on
Android, presumably as an undocumented implementation detail, but as
xamarin/monodroid@ed984a3a was trying to get things working within
the (now dead) Android Designer -- which ran using a Desktop JDK --
Android-specific extensions were not available.

Update `JniEnvironment.Types` to use `Class.forName(String)` instead
of `ClassLoader.loadClass(String)` to load Java classes, as a fallback
for when `JNIEnv::FindClass()` fails to find the class. 

`[Obsolete]` the `JniRuntime.CreationOptions.ClassLoader_LoadClass_id`
property as it is no longer used.

[0]: https://developer.android.com/reference/java/lang/Class#forName(java.lang.String,%20boolean,%20java.lang.ClassLoader)
[1]: https://developer.android.com/reference/java/lang/ClassLoader#loadClass(java.lang.String)

Fixes: dotnet/java-interop#23

Changes: dotnet/java-interop@bc44f08...5852e6e

  * dotnet/java-interop@5852e6e3: [Java.Interop] Use `Class.forName()` as fallback to load Java classes (dotnet/java-interop#1326)

Fixes: dotnet/java-interop#23

Changes: dotnet/java-interop@bc44f08...5852e6e

  * dotnet/java-interop@5852e6e3: [Java.Interop] Use `Class.forName()` as fallback to load Java classes (dotnet/java-interop#1326)