feat: Postgres-based meta database

[betodealmeida]

SUMMARY

Shillelagh can now use Postgres as a backend (via the Multicorn2 extension. This PR adds support for it to the meta database.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

1. Install the latest version of Shillelagh: pip install "shillelagh[all]>=1.3.0"
2. Run the docker container in the Shillelagh repo that has Multicorn2 installed: docker compose -f postgres/docker-compose.yml up
3. Add a new Superset Meta Database with the URI superset+multicorn2://shillelagh:shillelagh123@localhost:5432/shillelagh

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[rusackas]

This has sat untouched in draft mode for quite a while, so we'll go ahead and close it. We welcome you to reopen it if you want to contribute the change. Thank you for your contribution nonetheless!