IRCv3: Implement join and part message handlers
Review Request #3235 — Created June 7, 2024 and submitted — Latest diff uploaded
This only handle the RFC versions, we'll do extended-join later.
The TODO's are not meant to be done in this RR because they require additional code in IRCv3Connection, and once that's done we'll grab these then.
Connected to my local ergo and had another client join and part a few times while I verified that the member list was updated correctly.