change DOTNET_ to ASPIRE_ in config variables

[danmoseley]

Variables that are unique to Aspire (ie., not things like DOTNET_ROOT) should use ASPIRE_ not DOTNET_ as Aspire is a platform and toolset for building polyglot apps, this seems more appropriate.

At the moment it seems like that's these - all should have

DOTNET_ASPIRE_CONTAINER_RUNTIME // change to ASPIRE_CONTAINER_RUNTIME, etc
DOTNET_ASPIRE_DEPENDENCY_CHECK_TIMEOUT
DOTNET_ASPIRE_SERVICE_STARTUP_WATCH_TIMEOUT
DOTNET_ASPIRE_SHOW_DASHBOARD_RESOURCES
DOTNET_DASHBOARD_CONFIG_FILE_PATH // change to ASPIRE_DASHBOARD_CONFIG_FILE_PATH
DOTNET_DASHBOARD_CORS_ALLOWED_ORIGINS
DOTNET_DASHBOARD_FILE_CONFIG_DIRECTORY
DOTNET_DASHBOARD_FRONTEND_BROWSERTOKEN
DOTNET_DASHBOARD_OTLP_ENDPOINT_URL
DOTNET_DASHBOARD_OTLP_HTTP_ENDPOINT_URL
DOTNET_DASHBOARD_RESOURCE_SERVER_ENDPOINT_URL
DOTNET_DASHBOARD_RESOURCESERVICE_APIKEY
DOTNET_DASHBOARD_UNSECURED_ALLOW_ANONYMOUS

this needs to be done while still recognizing the old names. I see env vars all over the code - it might be a good time to centralize into some utility class.

incidentally noticed this is missing an underscore

aspire/playground/TestShop/MyFrontend/Program.cs

Line 13 in 07b7c74

var isHttps = Environment.GetEnvironmentVariable("DOTNET_LAUNCHPROFILE") == "https";

[danmoseley]

cc @DamianEdwards