## Problem
I need `neon_superuser` to be allowed to create snapshots for
replication tests
## Summary of changes
Adds a migration that grants these functions to neon_superuser
It makes them much easier to reason about, and allows other SQL tooling
to operate on them like language servers, formatters, etc.
I also brought back the removed migrations such that we can more easily
understand what they were. I included a "-- SKIP" comment describing why
those migrations are now skipped. We no longer skip migrations by
checking if it is empty, but instead check to see if the migration
starts with "-- SKIP".