[JavaTypeSystem] Enable resolving generic types on declaring types.

[jpobst]

Fixes #815.

Given Java like this:

public class MyClass<T>
{
    public class MyNestedClass<U>
    {
      public void DoT (T value) { }
      public void DoU (U value) { }
    }
}

ApiXmlAdjuster does not look for generic parameter types on parent types, resulting in the method DoT being removed:

api.xml.class-parse : warning BG8605: The Java type 'T' could not be found (are you missing a Java reference jar/aar or a Java binding library NuGet?)

java-resolution-report.log:

==== Cycle 1 ====

The method '[Method] void DoT(T p0)' was removed because the Java parameter type 'T' could not be found.

JavaTypeSystem supports this, but it was initially disabled to help ensure that it was producing the same output as ApiXmlAdjuster for testing purposes. We can now enable it.