[FEAT]: PGVector as a Vector store

[Stono]

What would you like to see?

It'd be great to be able to use PGVector as a vector store, this would make it really trivial to host HA vector stores both locally and on many cloud providers.

[timothycarambat]

This is #873, its been talked about but becomes a big cumbersome since we need everyone to use the same schema for vector storage or require them to config it - which is rife with errors.

If we have full PG support, then PGVector makes perfect sense as well since we could handle both in one DB interface