Multiple User Connections

[HexaField]

Summary

• replace UserId as peer identifier with PeerID
• refactor avatar spawning to allow multiple connections but only one avatar
• refactor authority to be peer driven instead of user driven
• refactor WebRTC channels to use PeerID instead of UserId

References

closes #7069

Checklist

• If this PR is still a WIP, convert to a draft
• ensure all checks pass
• When this PR is ready, mark it as "Ready for review"
• Changes have been manually QA'd
• Changes reviewed by at least 2 approved reviewer

QA Steps

List any additional steps required to QA the changes of this PR, as well as any supplemental images or videos.