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 (see #29006, commit 00e0658e77f66103ebdeb29def99dc9f937c049d), which is more robust.
Fixes #29030.