Remove all the extra accessor methods added by javac in support-leanback.

Change private methods to be package protected to avoid extra methods
that get added to be able to access them from inner classes.

This CL saves 469 methods in our jar.

Bug: 31075707
Change-Id: I68c8152d060c9f35c72a2d78c608a9bccd12c86e
70 files changed