Create pg_catalog wrapper for DataFusion catalog structure

[returnString]

We should support a minimal subset of Postgres' system metadata tables for automatic introspection in IDEs and data vis tooling.

[magick93]

This would be very helpful.

I'm trying to connect to https://github.com/roapi/roapi using postgres fdw but am unable to due to not having a pg_catalog and lack of a postgres user.

[returnString]

I had a branch a while back where I started investigating this in the context of getting this working for IDEs like DataGrip, but ran into a lot of stumbling blocks in terms of parsing some of the (frankly insane 😅) queries that these tools use to inspect metadata.

Haven't had a lot of time lately to work on this project, but potentially a good starting point for anyone who wants to pick up this work.

Edit: Also, that basic approach might be enough for something like an FDW - it's not something I've tested.

[returnString]

Revived and merged the pgcatalog branch (see here).

@magick93 lemme know if there's more metadata required for your use-case - it's pretty barebones atm, but it's a start :)