MSF - MoQ Streaming Format

HLS/DASH playlists suck. WebRTC SDP is even worse. MSF is a replacement for both, utilizing MoQ live streams.

MSF is a catalog format for MoQ. It's similar to the hang catalog and we'll probably merge them in the future.

We track draft-01, which changed the catalog version from a number to a "draft-XX" string and moved init data out of the track into a root initDataList referenced by initRef. Our implementation hides this on the wire: the catalog API is a version-agnostic snapshot, draft-00 catalogs still decode, and init data is always presented inline regardless of how it was carried.

Our implementation also carries an optional stalled boolean on video tracks as a non-standard extension shared with the hang catalog. It recommends temporarily avoiding a track without making that track unavailable.

See the draft for the latest details.