codec2: Implement gav1 decoder component

Note that this CL does not switch the default AV1 decoder to gav1
yet. That will be done in a follow-up.

Test: CTS media tests related to AV1 still pass.
Bug: 131989882
Bug: 130249450
Merged-In: Ifb88d0f51d85e59fa37d5cead8a5d4757067fedd
Change-Id: Ifb88d0f51d85e59fa37d5cead8a5d4757067fedd
3 files changed