Disable auth-source-pass-extra-query-keywords by default

Disable auth-source-pass-extra-query-keywords by default

* doc/misc/auth.texi: Mention subdomain matching in
`auth-source-pass-extra-query-keywords' section.
* etc/NEWS: Mention the loss of traditional auth-source-pass features
when `auth-source-pass-extra-query-keywords' is enabled.
* lisp/auth-source-pass (auth-source-pass-extra-query-keywords): Set
default to nil.  Mention domain matching in doc string.
(auth-source-pass--match-regexp): Allow username to contain "@".
* lisp/erc/erc-compat.el:
(erc-compat--29-auth-source-pass--retrieve-parsed): Adjust regexp.
* test/lisp/auth-source-pass-tests.el
(auth-source-pass-extra-query-keywords--suffixed-user): make plain
username more email-like.
(Bug#58985.)