[Mono.Android] Java.Lang.Object.GetObject<T>() implementation

[jonathanpeppers]

Context: #9630
Context: dotnet/java-interop#1295

As an alternative to #9630...

For NativeAOT support, implement Java.Lang.Object.GetObject() using the new JniRuntime.JniValueManager.GetPeer() method.

This also cleans up a few things if Java.Lang.Object introduces an internal DynamicallyAccessedMemberTypes Constructors field.

[jonpryor]

Draft commit message:

Context: https://github.com/dotnet/android/pull/9630
Context: https://github.com/dotnet/android/pull/9716
Context: https://github.com/dotnet/java-interop/commit/e288589d92afc9edd9070638ebed72f67e310117
Context: 

@jonathanpeppers attempted to prototype MAUI startup in a NativeAOT
environment, which promptly crashes similar to:

	E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.DllNotFoundException: DllNotFound_Linux, xa-internal-api, 
	E AndroidRuntime: dlopen failed: library "xa-internal-api" not found
	E AndroidRuntime: dlopen failed: library "libxa-internal-api" not found
	E AndroidRuntime: 
	E AndroidRuntime:    at System.Runtime.InteropServices.NativeLibrary.LoadLibErrorTracker.Throw(String) + 0x47
	E AndroidRuntime:    at Internal.Runtime.CompilerHelpers.InteropHelpers.FixupModuleCell(InteropHelpers.ModuleFixupCell*) + 0xe2
	E AndroidRuntime:    at Internal.Runtime.CompilerHelpers.InteropHelpers.ResolvePInvokeSlow(InteropHelpers.MethodFixupCell*) + 0x35
	E AndroidRuntime:    at Android.Runtime.RuntimeNativeMethods.monodroid_TypeManager_get_java_class_name(IntPtr) + 0x22
	E AndroidRuntime:    at Java.Interop.TypeManager.GetClassName(IntPtr) + 0xe
	E AndroidRuntime:    at Java.Interop.TypeManager.CreateInstance(IntPtr, JniHandleOwnership, Type) + 0x69
	E AndroidRuntime:    at Java.Lang.Object._GetObject[T](IntPtr, JniHandleOwnership) + 0x4e
	E AndroidRuntime:    at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) + 0x89
	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:1182)
	E AndroidRuntime: 	at android.app.ActivityThread.handleBindApplication(ActivityThread.java:6460)
	E AndroidRuntime: 	at android.app.ActivityThread.access$1300(ActivityThread.java:219)
	E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1859)
	E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:107)
	E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:214)
	E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7356)
	E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
	E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
	E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

because:

 1. MAUI apps provide an `Android.App.Application` sublass, and

 2. [`Application` is "special"][0], and

 3. When `Java.Lang.Object.GetObject<T>()` is hit for an instance
    which doesn't already have an instance mapping -- i.e.
    `Object.PeekObject()` returns `null` -- then we'd hit
    `TypeManager.CreateInstance()`, which is a codepath full of
    P/Invokes, and P/Invokes don't currently work on NativeAOT [^1].

The solution is to partially resuscitate PR #9630, but this time have
`Java.Lang.Object.GetObject<T>()` call
`Java.Interop.JniRuntime.JniValueManager.GetPeer()` instead of
`Java.Interop.JniRuntime.JniValueManager.GetValue()`; see also
dotnet/java-interop@e288589d.

This allows `Application` subclasses to be used (along with other
build system changes present in #9716).

This also cleans up a few things if `Java.Lang.Object` introduces an
internal `DynamicallyAccessedMemberTypes Constructors` field.

[0]: https://learn.microsoft.com/en-us/previous-versions/xamarin/android/internals/architecture#java-activation

[^1]: It's *not* that NativeAOT doesn't support P/Invokes; it does.
      The problem is that for a P/Invoke to work, we need to know the
      name of the native library we're P/Invoking into, and our
      NativeAOT sample environment doesn't include any `.so` files
      other than the one for the app, i.e. whatever we'd P/Invoke
      into doesn't exist.