Move most android.util.Mutable* classes to framework.

android.util is the only package shared between libcore and
framework, with only the Mutable* classes living in libcore.

This CL topic moves most of these classes to framework.
After this CL topic, only MutableInt and MutableLong remain
in libcore. This prevents future libcore dependencies on
android.util; it is a first step towards removing the package
overlap between libcore and framework.

Test: Treehugger
Bug: 67901714
Change-Id: I049b74a5ccd043c8e04b7657c649637c0a65aa50