Human matrix accounts come from SSO, not hivectl. Matrix homeserver
admin will come from authelia's admins group (sync tracked in #4585);
password reset moves to swarm level (#4798). promote-user and
reset-password were already broken from the hive: the hive's sender
account has no admin sender to call the admin room with, only the
swarm's does.
Removes the three hivectl matrix verbs, their HostRequest variants,
their hive-c0re handlers, and the admin-room helpers (discover room id,
send-and-poll, event-id extraction, password/success parsing) that
only they used. sync-admin and invite are unchanged.
Refs #4585
93bbec015f