journald: use structured message + catalog entry for disk usage

journald: use structured message + catalog entry for disk usage

The format of the journald disk usage log entry was changed back and
forth a few times. It is annoying to have a very verbose message, but
if it is short it is hard to understand. But we have a tool for this,
the catalogue.

$ journalctl -x -u systemd-journald
Jan 23 18:48:50 rawhide systemd-journald[891]: Runtime journal (/run/log/journal/) is 8.0M, max 196.2M, 188.2M free.
-- Subject: Disk space used by the journal
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Runtime journal (/run/log/journal/) is currently using 8.0M.
-- Maximum allowed usage is set to 196.2M.
-- Leaving at least 294.3M free (of currently available 1.9G of disk space).
-- Enforced usage limit is thus 196.2M, of which 188.2M are still available.
--
-- The limits controlling how much disk space is used by the journal may
-- be configured with SystemMaxUse=, SystemKeepFree=, SystemMaxFileSize=,
-- RuntimeMaxUse=, RuntimeKeepFree=, RuntimeMaxFileSize= settings in
-- /etc/systemd/journald.conf. See journald.conf(5) for details.
Jan 23 18:48:50 rawhide systemd-journald[891]: System journal (/var/log/journal/) is 480.1M, max 1.6G, 1.2G free.
-- Subject: Disk space used by the journal
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- System journal (/var/log/journal/) is currently using 480.1M.
-- Maximum allowed usage is set to 1.6G.
-- Leaving at least 2.5G free (of currently available 5.8G of disk space).
-- Enforced usage limit is thus 1.6G, of which 1.2G are still available.
--
-- The limits controlling how much disk space is used by the journal may
-- be configured with SystemMaxUse=, SystemKeepFree=, SystemMaxFileSize=,
-- RuntimeMaxUse=, RuntimeKeepFree=, RuntimeMaxFileSize= settings in
-- /etc/systemd/journald.conf. See journald.conf(5) for details.