As PEP bookmarks are nowadays used to sync joined state across devices, trigger points
have been added to XEP-0045 so XEP-0402 can automatically update the `autojoin` status on
MUC joining or leaving.
A check has been added to ignore already joined or left room when XEP-0402 plugin updates
the MUC status on bookmark update.
- Former bookmarks implementation is now labeled as "legacy".
- XEP-0402 is now used for bookmarks when relevant namespaces are found, and it fallbacks
to legacy XEP-0048/XEP-0049 bookmarks otherwise.
- CLI legacy bookmark commands have been moved to `bookmarks legacy`
- CLI bookmarks commands now use the new XEP-0402 (with fallback to legacy one
automatically used if necessary).