shell-completion: systemd-run: add missing options

Closes #19044.

(cherry picked from commit c23bb96b)
(cherry picked from commit e60fe377)

I'm not sure if all options listed in this patch are already there in v246… But
at least --slice-inherit which was originally requested in #19044 is here.
Worst case, users will get completion to some options which are not there yet.