rpm: add %systemd_postun_with_reload and %systemd_user_postun_with_reload

rpm: add %systemd_postun_with_reload and %systemd_user_postun_with_reload

For some units, the package would like to issue a reload. The machinery was
already in place since c9615f73521986b3607b852c139036d58973043c:

  systemctl reload-or-restart --marked

  Enqueues restart jobs for all units that have the 'needs-restart'
  mark, and reload jobs for units that have the 'needs-reload' mark.
  When a unit marked for reload does not support reload, restart will
  be queued.

The new macros allow a reload to be issued instead of a restart.

Based on the discussion on fedora-devel:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/IJSUGIEJNYZZRE53FF4YFUEBRHRAVIXR/

Tested using dummy package https://github.com/keszybz/rpm-test-reload.