crimson/net: unify the usage of entity_type_t and entity_name_t

crimson/net: unify the usage of entity_type_t and entity_name_t

* use standard entity_type_t(uint8_t) in favor of peer_type_t(int);
* use standard ceph_entity_type_name() to print where possible;
* use peer_name to encapsulate peer_type and peer_id in Connection.h;
* clean related interfaces in Messenger and Connection;
* print peer_name in Connection logging prefix;

Signed-off-by: Yingxin Cheng <yingxin.cheng@intel.com>