cron/jobs.py is already ~3400 lines; JOB_DEFINITION_FIELDS and
merge_job_definition are only used by importers of a foreign cron store
(profile distributions), so they live in a small dedicated module instead
of growing the scheduler file. profile_distribution imports the new module
directly; jobs.py is left byte-identical to main (no re-export shim).
Refs #120823
Co-authored-by: John Paul Soliva <soliva.johnpaul@icloud.com>
Co-authored-by: JoaoMarcos44 <joaomarcosdias444@gmail.com>