Add View reveal on focus hint

Provide a way for views to signal that they would prefer not
to have their parents scroll or otherwise rearrange when they
request focus to try to show the full focused view to the user.
In some cases this can be disruptive to the UX.

As of now, framework views do not respect this hint and custom
views such as those found in currently deployed support libs
don't either. The policy is left open to ViewParent subclasses
that implement requestChildFocus.

Bug 30256922

Change-Id: I55194de888fe2b8129be9a9aa21aa5e18cbb8296