Wrap PackageContext and SingletonContext

Wrap blueprint.PackageContext so that the *Func methods can provide
an android.Config instead of an interface{}.  The modified signatures
means that every method in ModuleContext and SingletonContext
that takes a blueprint.PackageContext now needs to be wrapped to
take an android.PackageContext.

SingletonContext wasn't previously wrapped at all, but as long
as it is, wrap everything like ModuleContext does.  This requires
updating every Singleton to use the android-specific methods.

Test: builds, all Soong tests pass
Change-Id: I4f22085ebca7def6c5cde49e8210b59d994ba625