libbinder: stricter APEX + VNDK stability checks

This is in preparation for splitting system/apex stability and also
ensures there are no surprises if/when vendor APEXes are introduced by
specifically checking that the only __ANDROID_APEX__ + __ANDROID_VNDK__
case is com.android.media, which is compiled with vendor code, but
shipped with the system partition.

Bug: 139325195
Test: build checks satifised, TEST_MAPPING
Change-Id: Id72e40addb4ab4b7a7e2e35a90c1ca0d0a51558a