C2SoftGav1Dec: Add support for 12-bit decoding

Supports 12-bit AV1 decoding to RGB1010102 and YV12 using libyuv
functions.

Also enables 12-bit AVIF decoding.

[1] Builds (with and without the libyuv update).
[2] AV1 CTS tests pass.
[3] 12-bit AV1 videos playback with exoplayer and files app (using sw decoder).
[4] 12-bit AVIF files are displayed properly in the files app.

Bug: 268505204
Test: [1][2][3][4]

Merged-In: If611003464fdbc7f41259a763f89e3771a885977
Change-Id: If611003464fdbc7f41259a763f89e3771a885977
(cherry picked from commit b9661b6b)