driver-adapters: Map neon errors to Prisma errors (#4213)

* driver-adapters: Map neon errors to Prisma errors

Approach taken: instead of duplicating error handling logic in TS, we
extract all information we need from the error and forward it to engine.
Engine is than reuses error parsing code from native driver.

`PostgresError` is intermediate form for storing this information.
It can be created from eithe `tokio_postgres` error or from JS. It then
gets parsed and converted to a `quaint:Error`.

This allows to handle most of the DB level errors (read: everything that
actually reached running DB). It does not handle TLS and networking
errors since these look completely different in JS. We'll need to handle
them later.

* Add hint & severity fields on TS side

quaint/src/connector/postgres.rs

@@ -1,5 +1,5 @@
 mod conversion;
-mod error;
+pub mod error;
 
 use crate::{
     ast::{Query, Value},