To be done not earlier than just before releasing v21.0.0 stable, or after there was a devXX bump.

• Remove ClientControlPacket::VideoErrorReport
• Merge ControlSocket with StreamSocket
• Refactor packet protocol
  • Make prefix data little-endian
  • Make packet length contain itself (add 4 bytes to the count)
  • Remove extra 4 bytes to the max shard length
• Send combined eye gaze with separate field
• Send eyes already in local head space.
• [ ] Use a json string in place of the VideoStreamingCapabilities packet. Using ext_str instead
• Make multimodal input protocol default
• [ ] Send velocity for skeletal hand tracking decided not to do/not needed
• [ ] Use mesh foveated rendering deferred. Needs protocol support to negotiate disabling FFE.
• [ ] Add static controller offsets on the client and make parameter exposed by dashboard default to [0,0,0] was done already in v20
• Include DecoderConfig packet in the video frame header, to avoid having to request another IDR and resend the DecoderConfig two times.
• Make all some stream header packets extensible with a Vec<u8> (don't use json) String decoded with json. Values can only be appended and not removed. Alternatively investigate CapnProto or Flatbuffers which support protocol extensions natively. overkill
• Use mutually exclusive tracking sources (e.g. 2 eyes or combined gaze, fb or htc face tracking, fb or pico body tracking), and wrap it with Option.
• Remove limited range encoding support
• Change dashboard API to not require a body for requests. This aligns better with the ureq 3.0 API, and standard HTTP practices
• Reorder settings: create SteamVR tab, rename headset to Tracking, for each tracking method, put source settings in Tracking and sink in SteamVR or Extra->Sinks (for example OSC/UDP/VMC)
• Switch to bincode 2.0