Use erc-display-message instead of erc-make-notice

Use erc-display-message instead of erc-make-notice

* lisp/erc/erc-backend.el (erc-server-JOIN): Let `erc-display-message'
handle formatting instead of baking out a string.  The text ultimately
inserted remains unchanged, but forwarding the original `format-spec'
arguments now has the side effect of influencing text properties, which
conveys richer meaning for modules to act upon when doing things like
deciding whether to hide a given message.
* lisp/erc/erc.el (erc-cmd-IGNORE, erc-cmd-UNIGNORE,
erc--unignore-user, erc-cmd-IDLE, erc-cmd-BANLIST, erc-cmd-MASSUNBAN):
Use `erc-display-message' with `notice' for the TYPE parameter instead
of composing `erc-make-notice' and `erc-display-line'.