Allow Activities to handle configuration changes

Make CONFIG_ASSETS_PATHS to public to allow activity itself to handle
assets paths config changes.
Introduce CONFIG_RESOURCES_UNUSED for applications that do not use
Resources at all like games to disabled all activity restart triggered
by any kind of configuration change.
Adding aapt2 support to allow app to handle all kinds of config change
based on the targeting SDK for more general cases.
Adding Framework host tests to test against non activity restart after
building and enabling frro.

Bug: b/180625460
Flag: android.content.res.handle_all_config_changes
Test: Added unit and CTS tests and verified all affected tests passed
Change-Id: I816df3604149ed337974ace83aef20d3d3566338