Correct support for avc3, hev1?

[dalecurtis]

• Apparently avc3 and hev1 are specific forms for writing the AVC and HEVC bitstreams.
• AVC1 and AVC3 don't differ much beyond the codec string, but HEV1 has a array_completeness value which should be set to 1 if parameter sets are expected to change.
• WebCodecs VideoEncoder requires explicit config changes, so no matter what we always emit AVC1/HVC1 compliant streams.

The WebCodecs codec registry currently reports support for both of these forms. Should we remove that? Should we require implementations to set array_completeness=1 for HEV1 content even if we don't allow in-band parameter set changes?

@Djuffin @sandersdan

[StaZhu]

I think if its hev1/avc3, WebCodec should also include sps/pps/vps into the EncodedVideoChunk, so I dont need to extract codec description to get these parameter sets if they are changed.