fix(App): wait to leave previous call before joining new one

[Antreesy]

☑️ Resolves

• Fix possible race condition
• Fix "Allow adding participants to one-to-one calls creating a new conversation" feature not working properly #15336

Example for switching rooms:

• leaveConversation might trigger leaveCall -> 'release webrtc media'
• joinConversation might be followed by joinCall -> 'start webrtc media'
• If processes are not executed in the right order, that might kill just started media and break joining the call

Drawbacks: longer visual switching.

AI (if applicable)

• Analysis of this PR was partly or fully done using AI

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
Screenshot before	Screenshot after

🚧 Tasks

• ...

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[danxuliu]

I have not tested it, but it makes sense 👍

If I am not mistaken (but I am speaking from memory, so take this with a pinch of salt) joining a new conversation implicitly leaves the old one, so a possible improvement might be to wait only if the user is active in a call, and otherwise just switch to the new conversation without waiting. This should solve the race condition when switching between calls and at the same time prevent the delays introduced with this fix when switching between conversations.

But as mentioned my assumption could be wrong and/or I could be missing other details, so fine by me to merge it as is even with the drawbacks and maybe improve it in a follow up.

[Antreesy]

/backport to stable33

[Antreesy]

/backport to stable32