_pico_peer_address: add new column "connection_type"

New column added in the _pico_peer_address system table, called "connection_type". It can be either iproto or pgproto

See: https://docs.picodata.io/picodata/devel/tutorial/monitoring/#reading_raft_leader_log

https://docs.picodata.io/picodata/devel/architecture/system_tables/#_pico_peer_address

Follow-up - picodata!1644 (merged)

See also - picodata#1237 (closed)