test: fix intermittent error in rpc_net.py (bitcoin#29030)

Asserting for the debug log message "Added connection peer=" is
insufficient for ensuring that this new connection will show up in a
following getpeerinfo() call, as the debug message is written in the
CNode ctor, which means it hasn't necessarily been added to
CConnman.m_nodes at this point.

Solve this by using the recently introduced `wait_for_new_peer`
helper, which is more robust.

Fixes bitcoin#29030.

test/functional/rpc_net.py

@@ -110,7 +110,7 @@ def test_getpeerinfo(self):
         no_version_peer_id = 2
         no_version_peer_conntime = int(time.time())
         self.nodes[0].setmocktime(no_version_peer_conntime)
-        with self.nodes[0].assert_debug_log([f"Added connection peer={no_version_peer_id}"]):
+        with self.nodes[0].wait_for_new_peer():
             no_version_peer = self.nodes[0].add_p2p_connection(P2PInterface(), send_version=False, wait_for_verack=False)
         self.nodes[0].setmocktime(0)
         peer_info = self.nodes[0].getpeerinfo()[no_version_peer_id]