[Mono.Android] Generate default interface members for API-30+ (#4353)

Context: dotnet/java-interop#509

Use `generator --lang-features=default-interface-methods` so that we
start binding [Java interface default methods][0] within `android.jar`
and `Mono.Android.dll`, for API-R.

*Note*: `Microsoft.DotNet.ApiCompat.exe` does not currently understand
C#8 [default interface members][1], which we use to bind Java interface
default methods.  As such, it reports an error for *every added*
default interface member, e.g.

	InterfacesShouldHaveSameMembers : Interface member 'Android.App.Application.IActivityLifecycleCallbacks.OnActivityPostCreated(Android.App.Activity, Android.OS.Bundle)' is present in the implementation but not in the contract.

We are investigating improving `Microsoft.DotNet.ApiCompat.exe` so
that it doesn't report such changes as incompatible.

[0]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html
[1]: https://github.com/dotnet/csharplang/blob/f7952cdddf85316a4beec493a0ecc14fcb3241c8/proposals/csharp-8.0/default-interface-methods.md

Author: jonpryor

src/Mono.Android/Android.Telephony.Mbms/IGroupCallCallback.cs

@@ -5,7 +5,7 @@
 
 namespace Android.Telephony.Mbms
 {
-	public interface IGroupCallCallback : IJavaObject
+	public partial interface IGroupCallCallback : IJavaObject
 	{
 		// This is not generated because all the methods in this
 		// interface are default interface mthods, and the interface

src/Mono.Android/Mono.Android.csproj

@@ -11,6 +11,7 @@
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>..\..\product.snk</AssemblyOriginatorKeyFile>
     <NoWarn>0618;0809;0108;0114</NoWarn>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <Import Project="..\..\Configuration.props" />
   <PropertyGroup>

src/Mono.Android/Mono.Android.targets

@@ -98,9 +98,10 @@
       <_Api>$(IntermediateOutputPath)mcw\api.xml</_Api>
       <_Dirs>--enumdir=$(IntermediateOutputPath)mcw</_Dirs>
       <_FullIntermediateOutputPath>$([System.IO.Path]::GetFullPath('$(IntermediateOutputPath)'))</_FullIntermediateOutputPath>
+      <_LangFeatures Condition="$(AndroidApiLevel) &gt;= 30">--lang-features=default-interface-methods</_LangFeatures>
     </PropertyGroup>
     <Exec
-        Command="$(ManagedRuntime) $(ManagedRuntimeArgs) $(Generator) $(_GenFlags) $(_ApiLevel) $(_Out) $(_Codegen) $(_Fixup) $(_Enums1) $(_Enums2) $(_Versions) $(_Annotations) $(_Assembly) $(_TypeMap) $(_Dirs) $(_Api)"
+        Command="$(ManagedRuntime) $(ManagedRuntimeArgs) $(Generator) $(_GenFlags) $(_ApiLevel) $(_Out) $(_Codegen) $(_Fixup) $(_Enums1) $(_Enums2) $(_Versions) $(_Annotations) $(_Assembly) $(_TypeMap) $(_LangFeatures) $(_Dirs) $(_Api)"
     />
     <ItemGroup>
       <Compile Include="$(_FullIntermediateOutputPath)\mcw\**\*.cs" KeepDuplicates="False" />

src/Mono.Android/metadata

@@ -1387,8 +1387,11 @@
   everything optional after API Level 26, but we cannot follow that yet.-->
   <remove-node path="/api/package/interface/implements[@name='java.lang.AutoCloseable']" />
 
-
-  <attr path="/api/package[@name='android.media']/interface[@name='MediaCas.EventListener']" name="argsType">MediaCasEventArgs</attr>
+  <!-- When there's only one method on the Interface (pre-API-30), this attribute goes on the Interface.
+       When there's more than one method on the Interface (API-30+), the attribute needs to go on the Method instead. -->
+  <attr api-until="30" path="/api/package[@name='android.media']/interface[@name='MediaCas.EventListener']" name="argsType">MediaCasEventArgs</attr>
+  <attr api-since="30" path="/api/package[@name='android.media']/interface[@name='MediaCas.EventListener']/method[@name='onEvent']" name="argsType">MediaCasEventArgs</attr>
+  
   <attr path="/api/package[@name='android.media']/interface[@name='MediaCas.EventListener']/method[@name='onEvent']/parameter[@name='MediaCas']" name="managedName">mediaCas</attr>
 
   <!-- Until API Level 26, android.graphics.Color was static. In API Level 26,
@@ -1551,4 +1554,10 @@
   <remove-node api-since="30" path="/api/package[@name='java.util']/interface[@jni-signature='Ljava/util/Map;']/method[@name='of' and count(parameter)=16]" />
   <remove-node api-since="30" path="/api/package[@name='java.util']/interface[@jni-signature='Ljava/util/Map;']/method[@name='of' and count(parameter)=18]" />
   <remove-node api-since="30" path="/api/package[@name='java.util']/interface[@jni-signature='Ljava/util/Map;']/method[@name='of' and count(parameter)=20]" />
+
+  <!-- Work around a generator bug where having multiple Listener methods with the same name cause multiple conflicting EventArgs classes to be created. -->
+  <!-- These are "default" method versions, so it's ok to remove them from an interface. -->
+  <remove-node api-since="30" path="/api/package[@name='android.animation']/interface[@name='Animator.AnimatorListener']/method[@name='onAnimationStart' and count(parameter)=2]" />
+  <remove-node api-since="30" path="/api/package[@name='android.animation']/interface[@name='Animator.AnimatorListener']/method[@name='onAnimationEnd' and count(parameter)=2]" />
+
 </metadata>