[Mono.Android] fix "replaceable" objects in ManagedValueManager

[jonathanpeppers]

The following test is failing on NativeAOT as well as any case we'd use ManagedValueManager:

[Test]
public void JnienvCreateInstance_RegistersMultipleInstances ()
{
using (var adapter = new CreateInstance_OverrideAbsListView_Adapter (Application.Context)) {
var intermediate = CreateInstance_OverrideAbsListView_Adapter.Intermediate;
var registered = Java.Lang.Object.GetObject<CreateInstance_OverrideAbsListView_Adapter>(adapter.Handle, JniHandleOwnership.DoNotTransfer);
Assert.AreNotSame (adapter, intermediate); // Passes
Assert.AreSame (adapter, registered); // Fails!
}
}

With the assertion:

Expected: same as <com.xamarin.android.runtimetests.CreateInstance_OverrideAbsListView_Adapter{cbd0e5a V.ED.VC.. ......I. 0,0-0,0}>
But was: <com.xamarin.android.runtimetests.CreateInstance_OverrideAbsListView_Adapter{cbd0e5a V.ED.VC.. ......I. 0,0-0,0}>

The second assertion fails because registered is the same instance as intermediate. In this example, this is a code path where intermediate should be "replaced" with adapter.

After lots of debugging, I found the problem are these lines in the ManagedValueManager.AddPeer() method:

var o = PeekPeer (value.PeerReference);
if (o != null)
return;

If we PeekPeer() in the middle of AddPeer() and a type is "replaceable", it would find an instance and not replace it! I did not find equivalent code in AndroidValueManager.AddPeer(), which is what is used in Mono & production today.

This was also addressed in Java.Interop's ManagedValueManager here:

• dotnet/java-interop@d3d3a1b

This also solves a test failure in Java.Interop-Tests:

Mono.Android.NET_Tests, Java.InteropTests.InvokeVirtualFromConstructorTests.CreateManagedInstanceFirst_WithNewObject / Release
Error message
Expected t and registered to be the same instance; t=20dfddd, registered=325d330
Expected: same as net.dot.jni.test.CallVirtualFromConstructorDerived@564f0f8
But was: net.dot.jni.test.CallVirtualFromConstructorDerived@564f0f8
Stack trace
at Java.InteropTests.InvokeVirtualFromConstructorTests.CreateManagedInstanceFirst_WithNewObject()
at System.RuntimeMethodHandle.InvokeMethod(ObjectHandleOnStack, Void**, ObjectHandleOnStack, BOOL, ObjectHandleOnStack)
at System.RuntimeMethodHandle.InvokeMethod(ObjectHandleOnStack, Void**, ObjectHandleOnStack, BOOL, ObjectHandleOnStack)
at System.RuntimeMethodHandle.InvokeMethod(Object, Void**, Signature, Boolean)
at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object, BindingFlags)