GenerateSystemUniqueListenerAddresses is a function that returns two listener addresses with unique ports per system and should be used to overwrite rpctest's default generator which is prone to use colliding ports.

NextAvailablePort returns the first port that is available for listening by a new node, using a lock file to make sure concurrent access for parallel tasks on the same system don't re-use the same port.

ListenerFormat is the format string that is used to generate local listener addresses.