[generator] Process Javadoc for nested types (#996)

Fixes: #992

Looking at the latest set of API docs for [a nested type][0] I noticed
that we were missing a lot of content that should have been produced by
the Mono.Android build when translating Javadoc to C# doc comments.

After further investigation, we realized that we were not attempting to
process and translate Javadoc for _any_ nested types.

Fix this oversight by adding a missing Javadoc processing iteration
over each type's nested types.

Additionally, Java documentation URLs for nested types have been fixed
by replacing `$` with `.` in both the URL and text for the URL.  This
replaces the previous URL of e.g.

	https://developer.android.com/reference/android/accessibilityservice/AccessibilityButtonController$AccessibilityButtonCallback

with:

	https://developer.android.com/reference/android/accessibilityservice/AccessibilityButtonController.AccessibilityButtonCallback

[0]: https://github.com/xamarin/android-api-docs/blame/b4084443c0354661e2257eb698e03d3fe1d86f1b/docs/Mono.Android/en/Android.AccessibilityServices/AccessibilityButtonController%2BAccessibilityButtonCallback.xml#L25

tools/generator/Java.Interop.Tools.Generator.ObjectModel/JavadocInfo.cs

@@ -257,9 +257,10 @@ static XElement CreateAndroidDocLinkUri (string prefix, string declaringJniType,
 			// Example: "https://developer.android.com/reference/android/app/Application#registerOnProvideAssistDataListener(android.app.Application.OnProvideAssistDataListener)"
 			// Example: "https://developer.android.com/reference/android/animation/ObjectAnimator#ofFloat(T,%20android.util.Property%3CT,%20java.lang.Float%3E,%20float...)"
 
+			declaringJniType = declaringJniType.Replace ("$", ".");
 			var java    = new StringBuilder (declaringJniType)
-				.Replace ("/", ".")
-				.Replace ("$", ".");
+				.Replace ("/", ".");
+
 			var url     = new StringBuilder (prefix);
 			if (!prefix.EndsWith ("/", StringComparison.Ordinal)) {
 				url.Append ("/");

tools/generator/Java.Interop.Tools.Generator.Transformation/JavadocFixups.cs

@@ -46,6 +46,9 @@ public static void Fixup (List<GenBase> gens, CodeGeneratorOptions options)
 
 			foreach (var type in gens) {
 				AddJavadoc (type, typeJavadocs, options.XmldocStyle);
+				foreach (var nested in type.NestedTypes) {
+					AddJavadoc (nested, typeJavadocs, options.XmldocStyle);
+				}
 			}
 		}