Plumbing for OPUS encoding.

Webm, OGG container extensions to hold opus.
hooks so we can say that we're recording in opus format.
OMX-specific changes are omitted since our target is Codec2

Bug: 111850384
Test: with separate omx routines
Change-Id: Iecb8b53df3fbd8506d2e6f007602284eb2d0decc