Add PostgreSQL as database target

[fritshoogland-yugabyte]

Hi, have you considered adding other databases to this tool?
I like your work and detail on making sure a thread can run without being blocked.
One of the main databases I am working with is PostgreSQL.

[pkolaczk]

This is a long term goal and it would require introducing a new abstraction layer and redesigning quite some things.
I considered it long time ago when started this project and I remember lack of async traits made it quite hard to have pluggable async drivers. But now Rust async is in a lot better shape and I can reconsider this.

Beware though, this is a large task, and considering a very limited amount of (unpaid) time I have to work on this project, this isn't going to happen soon.