Create .NET version of JcwGen-Tests.

[jpobst]

Create a .NET version of Xamarin.Android.JcwGen-Tests. It currently isn't possible to multi-target our test projects, so this creates a copy and uses $(AndroidJavaSource) to simplify the test suite by eliminating the Xamarin.Android.McwGen-Tests project and its custom MSBuild logic. This new version uses the more descriptive Xamarin.Android.BindingRuntime_Tests project name.

This ports 34 of the 41 tests in JcwGen-Tests. The remaining tests require additional projects to be ported to .NET to run successfully or require additional custom MSBuild logic from JcwGen to be ported.

Additionally, stop running this suite on Classic test agents in main.

We are choosing to not prioritize the remaining tests at this point and committing what we already have.

The unported tests are tracked in #7794.

[jonpryor]

The addition of tests/BindingTests/Xamarin.Android.BindingRuntime-Tests/Jars/org.jetbrains.kotlin.kotlin-stdlib.jar seems odd to me; why don't we instead reference the Xamarin.Kotlin.Stdlib NuGet package?

[jonpryor]

Context: https://github.com/xamarin/xamarin-android/issues/7794

Create a .NET version of
`tests/CodeGen-Binding/Xamarin.Android.JcwGen-Tests`.  It currently
isn't possible to multi-target our test projects, so instead create a
copy and use `@(AndroidJavaSource)` to simplify the test suite by
eliminating the `Xamarin.Android.McwGen-Tests` project and its custom
MSBuild logic.

This new version uses the more descriptive
`Xamarin.Android.BindingRuntime_Tests` project name.

This ports 34 of the 41 tests in `Xamarin.Android.JcwGen-Tests`.
The remaining tests require additional projects to be ported to .NET
to run successfully or require additional custom MSBuild logic from
`Xamarin.Android.JcwGen-Tests` to be ported.

Additionally, stop running this suite on Classic test agents on `main`.

We are choosing to not prioritize the remaining tests at this point
and committing what we already have.

The unported tests are tracked in #7794.

[pjcollins]

One last thought -- rather than creating a copy of all of the Java sources used by the tests, should we instead link to the files that already exist in the other test directory (for example https://github.com/xamarin/xamarin-android/tree/main/tests/CodeGen-Binding/Xamarin.Android.McwGen-Tests/java/com/xamarin/android)? I'm assuming the java sources are unchanged and could be shared?

If so, should we do the same for the test files as well? We could wrap any test changes or ignored tests in a #if NET6_0_OR_GREATER if we wanted to use the same files to help preserve git history.

[jpobst]

Honestly, we could just remove the old files and they would show up as moved files. This PR created a copy because it was originally done before we started removing Classic from main.

[jpobst]

Replaced with #7949.