fix(NewConversationDialog): speed up conversation creation flow

[Antreesy]

☑️ Resolves

• Fix Participant list is only displayed after some time #12206
• Only createConversation is mandatory to be completed first, rest request are secondary and could be done in parallel
• As owner of conversation definitely has all needed permissions and access to the conversation, we can fetch participants list (with statuses, permissions, e.t.c) much earlier
  • we don't need to wait to join conversation
  • we're the only one in the conversation yet, so don't need to debounce request (up to 3-15 sec)

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

Testing the time (with local server) from submitting the form with following:

• Description
• Avatar
• Password
• Listable
• 5 participants

to the time participants are fetched

🏚️ Before	🏡 After

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖥️ Tested with Desktop client or should not be risky for it
• 🖌️ 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

[ShGKme]

cc @nickvergessen
It seems we need too many requests to create a conversation. Can we add a new entrypoint / extend existing to do everything in one/two requests instead 5 + n where N is the number of participants?

[Antreesy]

Can we add a new entrypoint / extend existing

Previous discussion in #2874

[Antreesy]

/backport to stable29