ANDROID: GKI: enable KMI enforcement

Add android/abi_gki_aarch64.stg as initial ABI representation of the
KMI and start enforcing KMI. Kernel is not trimmed yet, the trimming
will be enabled after adding symbols lists.

This is not KMI freeze. While this is hard enforcement in the code
base, we still allow controlled changes to the ABI.

Test: TH
Bug: 269323432
Change-Id: Ic3a126a6d60242ae713ae396bb239af5b3e58c53
Signed-off-by: Aleksei Vetrov <vvvvvv@google.com>