Move ModuleContext.ModuleBuild to ModuleContext.Build

Now that android.ModuleContext does not include blueprint.ModuleContext
we can rename android.ModuleContext.ModuleBuild to
android.ModuleContext.Build without colliding with
blueprint.ModuleContext.Build.  Leave ModuleBuild as a wrapper around
Build for now to avoid having to update all the users outside
build/soong simultaneously.

Test: m checkbuild
Change-Id: I18eb8cc04faf002049a11d9aac97e9732ff5d638