Example for disabling changes at test time

Add test for the CompatChangeRule using dummy apis, gated using both
available APIs (Compatibility and IPlatformCompat). There's no need to
actually have these compat changes defined, since CompatChangeRule will
inject them regardless.

Bug: 140367850
Test: atest Gating
Change-Id: I3d41925fc579d5212100d9c081cd290f18efa43b