Unwind from fork and rebrand

[zth]

We've started diverging enough from pgtyped to actually drop the efforts of keeping this an actual fork. Plus, pgtyped is not actively developed anymore. So, I think we can unwind from trying to keep this a fork that's easy to pull upstream changes from, and rebrand this properly into its own thing. Maybe rescript-postgres or some other better name.

Will allow us to do a bunch of refactors and cleanups as well.