Add Activity.registerActivityLifecycleCallbacks()

As an alternative to requiring developers
register/unregister ActivityLifecycleCallbacks
at the Application level, provide the same API
at the Activity level.

This allows you to get lifecycle callbacks scoped
to only a single Activity without overriding
each individual callback.

The callbacks are purposefully nested within
the Application scoped ActivityLifecycleCallbacks.

Test: new CTS test
BUG: 116118635
Change-Id: Iab6d841019010a0bf9d91fe889db82e0135b4b9c