libstagefright: Add support for muxing Opus files to Ogg format with unified CSD

Now Ogg writer supports muxing opus files sent with either single
unified CSD or 3 CSDs that are returned by Ogg extractor.

Test: Tested using a local native application using AMediaMuxer API
Bug: 115576456
Change-Id: I335b078a4edf059aca6b3fd0f17b6bab3e006615