profiles: firefox: add new ~/.config/mozilla dir (#7061)

Default directories in Firefox 146 and earlier:

* ~/.cache/mozilla  # cache files
* ~/.mozilla        # config and data

In Firefox 147[1]:

* ~/.cache/mozilla  # cache files
* ~/.config/mozilla # config and data

Note that the new location apparently contains the same files as in the
former location (including settings, bookmarks, extensions, etc).
That is, even though the new directory resides in `$XDG_CONFIG_HOME` /
~/.config, it is not solely used for program configuration as described
in the XDG Base Directory specification[2] and `$XDG_DATA_HOME` /
~/.local/share/mozilla is seemingly not used at all (see also the
discussion in the bug tracker[3]).

Commands used to search and replace:

    $ perl -pi -e 's/(.* )(\${HOME}\/\.mozilla)(.*)/$1\${HOME}\/.config\/mozilla$3\n$1$2$3/' \
      -- \
      etc/inc/*.inc \
      etc/profile*/*.profile \

Note: The entries in the following profiles were sorted manually:

* etc/inc/disable-common.inc
* etc/inc/disable-programs.inc
* etc/profile-a-l/keepassxc.profile
* etc/profile-a-l/krunner.profile
* etc/profile-m-z/seamonkey.profile

Relates to #7040.

[1] https://www.firefox.com/en-US/firefox/147.0/releasenotes/
[2] https://specifications.freedesktop.org/basedir/latest/
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=259356

etc/profile-a-l/fluffychat.profile

@@ -23,7 +23,9 @@ include disable-xdg.inc
 # The lines below are needed to find the default Firefox profile name, to allow
 # opening links in an existing instance of Firefox (note that it still fails if
 # there isn't a Firefox instance running with the default profile; see #5352)
+noblacklist ${HOME}/.config/mozilla
 noblacklist ${HOME}/.mozilla
+whitelist ${HOME}/.config/mozilla/firefox/profiles.ini
 whitelist ${HOME}/.mozilla/firefox/profiles.ini
 
 mkdir ${HOME}/.local/share/fluffychat