Improve resiliance of SDK clients against server errors when searching a chat stored in the RAM:

Ensure that linphone_core_search_chat_room_2 doesn't do a SIP address comparison as stated in the RFC. In fact, doing that leads to being too exposed to server instabilities.
For example, if a server for whatever reason removes the conf-id parameter from the chatroom peer address, it will prevent to client to join any new chatroom as all will match the corrupted chat

Add class ConferenceContext to easily compare two chatrooms or
conference based on the parameters, local and remote address and the
participants