socket: Introduce API osmo_sock_multiaddr_get_name_buf()

An extra osmo_multiaddr_ip_and_port_snprintf() API is introduced which
is used by osmo_sock_multiaddr_get_name_buf() but which will also be
used by other app uers willing to use
osmo_sock_multiaddr_get_ip_and_port() according to its needs (eg. only
printing the local side).

Related: SYS#6636
Change-Id: I48950754ed6f61ee5ffa04a447fab8903f10acc0
diff --git a/TODO-RELEASE b/TODO-RELEASE
index e365746..316c0ec 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -8,7 +8,7 @@
 # If any interfaces have been removed or changed since the last public release: c:r:0.
 #library	what			description / commit summary line
 core      ADD       osmo_sock_multiaddr_{add,del}_local_addr()
-core      ADD       osmo_sock_multiaddr_get_ip_and_port()
+core      ADD       osmo_sock_multiaddr_get_ip_and_port(), osmo_multiaddr_ip_and_port_snprintf(), osmo_sock_multiaddr_get_name_buf()
 core      ADD       gsmtap_inst_fd2() core, DEPRECATE gsmtap_inst_fd()
 isdn		ABI change		add states and flags for external T200 handling
 gsm		ABI change		add T200 timer states to lapdm_datalink