How to access the MAST cache

Repost from Slack: I have used astroquery to download and cache TESS FFI cutouts with the `TessCut` class. Is there a way to iterate over files in the astroquery-MAST cache, rather than re-querying for the cutouts with `Tesscut.get_cutouts`?

Start by reading the TessCut class and the code behind Tesscut.get_cutouts to understand how the astroquery-MAST cache is stored. Determine whether cached TESS FFI cutouts can be enumerated without issuing a new query. Done means providing a documented way to iterate over matching cached files.

Written by the indexing model from the issue text.