core: move unit_status_emit_starting_stopping_reloading() and related calls to job.c
    
    This call is only used by job.c and very specific to job handling.
    Moreover the very similar logic of job_emit_status_message() is already
    in job.c.
    
    Hence, let's clean this up, and move both sets of functions to job.c,
    and rename them a bit so that they express precisely what they do:
    
    1. unit_status_emit_starting_stopping_reloading() →
       job_emit_begin_status_message()
    2. job_emit_status_message() → job_emit_done_status_message()
    
    The first call is after all what we call when we begin with the
    execution of a job, and the second call what we call when we are done
    wiht it.
    
    Just some moving and renaming, not other changes, and hence no change in
    behaviour.
    
    (cherry picked from commit 33a3fdd9781329379f74e11a7a2707816aad8c61)
    
    Related: #1737283
    
    patch_name: 0376-core-move-unit_status_emit_starting_stopping_reloadi.patch
    present_in_specfile: true
    location_in_specfile: 376
    squash_commits: true