* Rename "broadcast list" to "channel"/"broadcast channel" both in UI and code
* feat: Add new channel types
* Update CHANGELOG.md
* adb's review
* refactor: Rename BroadcastChannel to Broadcast
* Revert accidental change
* Make it possible to leave channels
- In a chat, if the chat is an InBroadcast, and it's not a contact
request, then the `Leave` menu option is shown with the translated
stock string `menu_leave_channel` as its label.
- If the user clicks on it, the confirmation dialog has
`menu_leave_channel` (rather than `menu_leave_group`) as its positive
option.
Counterpart of https://github.com/chatmail/core/pull/6984.
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Co-authored-by: adbenitez <asieldbenitez@gmail.com>
Co-authored-by: adb <adb@merlinux.eu>
