Fix for Sorting and Upserts

[bitner]

• Fix for issue with sorting (Malformed query when using multiple sort fields and token #152 )
• Fix for Upserts using items_staging_upsert table or upsert_item function.
• Add ability to merge enum, min, and max from queryables where collections have different values.
• Add tooling in pypgstac and pgstac to add stac_extension definitions to the database.
• Modify missing_queryables function to try to use stac_extension definitions to populate queryable definitions from the stac_extension schemas.
• Add validate_constraints procedure
• Add analyze_items procedure
• Add check_pgstac_functions function

[bitner]

Hmm, I can't duplicate the black error locally that is failing in the tests (on a file that was not updated).

[mmcfarland]

Not sure why, but it looks like the CI script is installing a 23.* version of black instead of the pinned version. Might be easiest to just update the version of black, run /format and commit.