processing tables for zpix

Add the equivalent of processing tables for zpix to make it easier to track which healpix were generated by which jobs and their success/failure state. Since one zpix job is responsible for multiple healpix, and subsequent resubmissions can change that mapping, I think we want this table to be one row per healpix, and the same jobid could appear in multiple rows.

`desi_healpix_redshifts` should initially populate this table (perhaps one table per SURVEY-PROGRAM), and `desi_resubmit_zpix` should be updated to use this table instead of parsing slurm scripts to know what healpix it was working on.