test: remove CNodeNoVersionMisbehavior from p2p_leak.py
It's also clearer to have no_version_disconnect_node send a message
other than version or verack in order to reach the peer discouragement
threshold.
test: remove CNodeNoVersionIdle from p2p_leak.py
test: Distinguish between nodes(bitcoind) and peers(mininodes) in p2p_leak.py
Also, remove "C" prefix from class names to match new style
This is a backport of core#19727