The irctest controller's registerUser sends NickServ REGISTER as a single
PRIVMSG, so a password that overflows the 512-byte line limit gets
truncated on the wire and can never match a later SASL login. Raise
NotImplementedByController for those, like the reference services
controllers, so such cases skip instead of failing spuriously.
The UID introduction omitted the second user field (insp sends both a real and a
displayed user), and the parser didn't strip IRCv3 message-tag prefixes, so
tagged PRIVMSGs addressed to a service were dropped. With both fixed a service
links to a real insp4 uplink and answers commands. Adds an irctest services
controller so this is verified against an isolated, throwaway ircd.
