RTC: [Interface] Error / disconnection modal enhancements

[maxschmeling]

Error modal states should be standardized across sync providers. If a provider emits a disconnected status, the resulting user interaction and messaging should be identical, no matter if the user is connected via HTTP polling, WebSocket, WebRTC, etc.

Statuses:

• connection-error
• disconnected
• collaborator limit exceeded
• ???

[chriszarate]

@shekharnwagh Can we consider this done? Can you link merged PRs and enumerate any remaining tasks?

[shekharnwagh]

I've mentioned this issue in PR #75066 which added disconnection modal. The disconnection messages could use review especially from @dabowman

[alecgeatches]

@shekharnwagh David got a pass on the messages in #75970.