framework/av,C2SoftGav1Dec: update to libgav1 v0.16.0

this is dependent on the update to external/libgav1 (ag/12016847,
change-id I63361c388d8cf6f652774b07c9475c45951599c5)

Bug: 162267932
Test: playback, cts on sargo-userdebug / sargo_hwasan-userdebug
Test: aosp_arm-eng aosp_arm64-eng aosp_x86-eng aosp_x86_64-eng build
Change-Id: Idc713f4b10776cfb6b7fa2d75b2162c3b85d3313
(cherry picked from commit 4f5bdb78)