Convert associated abspaths

[juzen2003]

Changes made:

• Add rules for ASSOCIATIONS (associations_to_bundles, associations_to_previews, associations_to_metadata, associations_to_documents)
• Add tests for those rules except associations_to_metadata since we need to create the index files for them
• Update run_tests_coverages.sh to run only pds3 tests when use_shelves_only is True because we don't have shelves for pds4 yet
• Replace all holdings with cls.PDS_HOLDINGS in pdsfile.py
• Create previews, documents, calibrated, metadata directories at the same level as bundles in Dropbox
  • Please review the structure of reviews, documents, calibrated, metadata directories and see if they make sense.

Known issues:

• For uranus under documents directory, it's currently empty. No ideas what files we should put here.
• For metadata directories, we need to create new index files, will have to work on the script under validationdirectory.

[juzen2003]

• Merge current main branch
• Rename PDS_HOLDINGS_DIR to PDS3_HOLDINGS_DIR
• Add test cases for associations_to_metadata rules for uranus_occs_earthbased (test_associated_abspaths)
• Create two index files for data/rings and data/global:
  • Pds4FileTest/pds4-holdings/metadata/uranus_occs_earthbased/uranus_occ_u0_kao_91cm/occ_rings.csv
  • Pds4FileTest/pds4-holdings/metadata/uranus_occs_earthbased/uranus_occ_u0_kao_91cm/occ_global.csv

[juzen2003]

Update based on comments:

• Add test case for metadata associated abspaths to test on the pdsfile instance of the entire bundle. Commented out test cases that test on the pdsfile instance of a data file (These will work when we add index shelf files later on)
• Replace .format with f string interpolation in pdsfile.py
• Simplify run_tests_coverage.sh