Build ShapePipe per-CCD failure mask #836

Build a per-CCD map of where shape measurement failed (PSF-model failure, etc.): ShapePipe records attempted/passed CCDs at run end, then a healsparse mask is built from CCD WCS corners as a pipeline step. Mike has code for this. Possibly (partially) closed by #797 (coverage nexp masks). Open question: confirm whether the observed half-CCD-sized failure chunks are a genuine sub-CCD failure mode or an artifact of how the catalogue was inspected.

Context: Paris meeting notes