WS-2379: Spectral cube ingestion

This adds changes to the image ingestion within ingest_envoy needed to ingest spectral cubes.

Spectral cubes are *cube*.fits files that can be a product of the std_calibration_and_imaging workflow, but it's not obvious when cubes images will be produced before CASA is run. These images are appended to the standard image manifest as extra science+ancillary products that will be picked up by ingest.

The image collection script from wf_framework has also been rewritten in Python with tests.

The unit tests mainly cover the collector and manifest generation, manual testing is ongoing.

There is a new path in ingest_envoy that was going to be used for spectral cubes but has been relabeled to be used by VLASS cubes in the future.