If the machine was suddenly shutted down (hard reboot for example) while
processing core dump, temp files created manually (not with a O_TEMPFILE flag)
stay in the system. After reboot systemd-coredump treat them as usual files, so
they wouldn't be rotated and shall pollute the filesystem.
Solution is to simply add those temp files to systemd-tmpfiles configs.
tmp.conf was dealing with 2 different kind of paths: one dealing with general
temporary paths such as /var/tmp and /tmp and the other one dealing with
temporary directories owned by systemd.
If for example a user wants to adjust the age argument of the general paths
only, he had to overload the whole file which is cumbersome and error prone
since any future changes in tmp.conf shipped by systemd will be lost.
So this patch splits out tmp.conf so the systemd directories are dealt
separately in a dedicated conf file. It's named "systemd-tmp.conf" based on the
naming recommendation made in tmpfiles.d man page.
In practice it shouldn't cause any regression since it's very unlikely that
users override paths owned by systemd.
Krayushkin Konstantin