[FEATURE]: Allow using a promise as a password for postgres

### Feature hasn't been suggested before.

- [x] I have verified this feature I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

Both node-postgres and postgres.js allow providing a Promise instead of a string as a password.
Drizzle-kit's validation rejects the config if a promise is used as password.

E.g. RDS with IAM authentication uses asynchronous, dynamically generated tokens as password, so we can't currently use all the drizzle-kit features that require access to the database, like Studio