Improvements to Talk conversation creation

[hamza221]

Is your feature request related to a problem? Please describe.

• If meeting is intended for internal users, new room shouldn't be public, but listable (open for users to join).
• Creation can be deferred, to fill room with event attendees afterwards
• In case it's public, (or has email attendees, and should be public atm), and password policy is enforced on instance, it would still fail, so need to be checked in UI
• in UI use 'Talk conversation' rather than 'Talk room' -> addressed in fix: close modal after creating conversation #6658

Describe the solution you'd like

👆

Describe alternatives you've considered

No response

Additional context

No response