[TrimmableTypeMap] Make JavaPeerProxy ctor accessible to typemaps

Generated typemap proxy types can derive directly from the non-generic JavaPeerProxy base when they need to represent interfaces or open generic definitions. Make the base constructor protected so those generated proxies can call it from typemap assemblies.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: simonrozsival

src/Mono.Android/Java.Interop/JavaPeerProxy.cs

@@ -42,7 +42,7 @@ public sealed class JavaPeerAliasesAttribute : Attribute
 	[AttributeUsage (AttributeTargets.Class | AttributeTargets.Interface, Inherited = false, AllowMultiple = false)]
 	public abstract class JavaPeerProxy : Attribute
 	{
-		private protected JavaPeerProxy (string jniName, Type targetType)
+		protected JavaPeerProxy (string jniName, Type targetType)
 		{
 			ArgumentNullException.ThrowIfNull (jniName);
 			ArgumentNullException.ThrowIfNull (targetType);