Allow desi_proc_night to submit only redshift jobs or desi_zproc to add entries to processing table

[akremin]

For daily operations, it is sometimes the case that we remove data from an old night and need to rerun cumulative redshifts on a later night.

As of now there is now "easy" way to resubmit the later cumulative night without human editing of tables or removing the spectral processing on that later night (even though the exposure-level data on the later night is independent).

See whether we can easily add logic in desi_proc_night to handle this case, or alternatively add processing_table logic to desi_tile_redshifts or desi_zproc