Merge PR #23338 into master

Merge PR #23338 into master

* refs/pull/23338/head:
	msg/Messenger: send_message -> send_to
	msg/msg_types: add entity_addr_t::legacy_or_front_addr()
	mon/MonMap: kill get_inst()
	mon: kill MonMap::get_inst() users
	mon/MonClient: replace get_mon_{addr,inst} with get_mon_addrs
	mon/MonClient: get_connection -> connect_to_mon
	src/test: get_connection -> connect_to_*
	mon/MonMap: add get_addrs() (temp wrappers)
	msg/Messenger: make connect_to() key method, get_connection() becomes wrapper