Update test package versions and add MSTest dependencies

Updated Microsoft.NET.Test.Sdk to version 17.12.0 and xUnit to 2.9.2 for improved compatibility and performance. Deprecated Microsoft.CSharp and introduced MSTest.TestAdapter and MSTest.TestFramework at version 3.6.3 to enable MSTest capabilities.

Author: ivandrofly

Directory.Packages.props

@@ -5,9 +5,11 @@
     <NoWarn>$(NoWarn);NU1507</NoWarn>
   </PropertyGroup>
   <ItemGroup>
-    <PackageVersion Include="Microsoft.CSharp" Version="4.7.0" />
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="16.0.0-preview-20190203-03" />
-    <PackageVersion Include="xunit" Version="2.4.1" />
-    <PackageVersion Include="xunit.runner.visualstudio" Version="2.4.1" />
+<!--    <PackageVersion Include="Microsoft.CSharp" Version="4.7.0" />-->
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageVersion Include="MSTest.TestAdapter" Version="3.6.3" />
+    <PackageVersion Include="MSTest.TestFramework" Version="3.6.3" />
+    <PackageVersion Include="xunit" Version="2.9.2" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.0-pre.49" />
   </ItemGroup>
 </Project>