[generator] Add more [ObsoleteOSPlatform] to prevent CA1422 (#1078)

Context: dotnet/android#7590
Context: dotnet/android@7004467

While building `Mono.Android.dll`, we had 1462 `CA1422` warnings of the
following caused by an interface being marked as `[ObsoleteOSPlatform]`
but the interface invoker class is not similarly annotated:

	…\xamarin-android\src\Mono.Android\obj\Debug\net8.0\android-33\mcw\Org.Apache.Commons.Logging.ILog.cs(128,11): 
	warning CA1422: This call site is reachable on: 'Android' 21.0 and later.
	'ILog' is obsoleted on: 'Android' 22.0 and later (This class is obsoleted in this android platform).

There were also 42 `CA1422` warnings caused by interface async
extension classes not having `[ObsoleteOSPlatform]` attributes:

	…\xamarin-android\src\Mono.Android\obj\Debug\net8.0\android-33\mcw\Org.Apache.Http.IO.ISessionOutputBuffer.cs(52,58):
	warning CA1422: This call site is reachable on: 'Android' 21.0  and later.
	'ISessionOutputBuffer.Write(byte[]?, int, int)' is obsoleted on: 'Android' 22.0 and later (This class is obsoleted in this android platform).

These warnings were disabled in dotnet/android@70044670.

Fix these warnings by adding the `[ObsoleteOSPlatform]` attribute to
these types if the source interface is deprecated.

tests/generator-Tests/Unit-Tests/CodeGeneratorTests.cs

@@ -611,6 +611,36 @@ public void ObsoletedOSPlatformAttributeUnneededSupport ()
 			Assert.True (writer.ToString ().Contains ("[global::System.Obsolete (@\"This method has an invalid deprecated-since!\")]"), writer.ToString ());
 		}
 
+		[Test]
+		public void ObsoletedOSPlatformAttributeInterfaceInfrastructureSupport ()
+		{
+			var xml = @"<api>
+			  <package name='com.xamarin.android' jni-name='com/xamarin/android'>
+			    <interface abstract='false' deprecated='This interface was deprecated in API-25' final='false' name='MyType' static='false' visibility='public' jni-signature='Lcom/xamarin/android/MyType;' deprecated-since='25' />
+			  </package>
+			</api>";
+
+			options.UseObsoletedOSPlatformAttributes = true;
+
+			var gens = ParseApiDefinition (xml);
+			var iface = gens.OfType<InterfaceGen> ().Single (g => g.Name == "IMyType");
+
+			generator.Context.ContextTypes.Push (iface);
+			var invoker = new InterfaceInvokerClass (iface, options, generator.Context);
+			var extensions = new InterfaceExtensionsClass (iface, iface.Name, options);
+			generator.Context.ContextTypes.Pop ();
+
+			// Ensure attribute was added to invoker class
+			var invoker_attribute = invoker.Attributes.OfType<ObsoletedOSPlatformAttr> ().Single ();
+			Assert.AreEqual ("This interface was deprecated in API-25", invoker_attribute.Message);
+			Assert.AreEqual (25, invoker_attribute.Version);
+
+			// Ensure attribute was added to extensions class
+			var extensions_attribute = invoker.Attributes.OfType<ObsoletedOSPlatformAttr> ().Single ();
+			Assert.AreEqual ("This interface was deprecated in API-25", extensions_attribute.Message);
+			Assert.AreEqual (25, extensions_attribute.Version);
+		}
+
 		[Test]
 		public void ObsoleteGetterOnlyProperty ()
 		{

tools/generator/SourceWriters/InterfaceExtensionsClass.cs

@@ -18,6 +18,8 @@ public InterfaceExtensionsClass (InterfaceGen iface, string declaringTypeName, C
 			IsStatic = true;
 			IsPartial = true;
 
+			SourceWriterExtensions.AddObsolete (Attributes, iface.DeprecatedComment, opt, iface.IsDeprecated, deprecatedSince: iface.DeprecatedSince);
+
 			foreach (var method in iface.Methods.Where (m => !m.IsStatic)) {
 				if (method.CanHaveStringOverload) {
 					// TODO: Don't allow obsolete here to match old generator.

tools/generator/SourceWriters/InterfaceInvokerClass.cs

@@ -32,6 +32,8 @@ public InterfaceInvokerClass (InterfaceGen iface, CodeGenerationOptions opt, Cod
 				MemberType	    = (!ji) ? null : (MemberTypes?) MemberTypes.TypeInfo,
 			});
 
+			SourceWriterExtensions.AddObsolete (Attributes, iface.DeprecatedComment, opt, iface.IsDeprecated, deprecatedSince: iface.DeprecatedSince);
+
 			Fields.Add (new PeerMembersField (opt, iface.RawJniName, $"{iface.Name}Invoker", false));
 
 			if (!ji) {