Make PackageManagerInternal#getPackageUid internal

Previous implementation was a direct callthrough to the public facing
method. This change deprecates the original method and introduces a new
method with the "Internal" suffix until we can clean up all uses of the
existing method.

Test: boots
Bug: 142386643
Change-Id: I86f92508f0236dbe611ac895fec0ad94f8e80afe