Replace refinery with our own backwards compatible migration code

[serprex]

Currently server_tests must be run with --test-threads=1 because of two things:

1. port collision
2. concurrent migrations failing

I explored fixing these in #926. Ports are easily solved, but migrations are a pain

This migration code works around concurrency with two changes from refinery:

1. ignore unique constraint violation from CREATE TABLE IF NOT EXISTS
2. lock migration table so concurrent migrations are serialized

Considered submitting a PR to refinery with these two fixes,
but this simple change was non trivial since they support multiple async/sync database drivers

[serprex]

Two aspects are implemented more loosely here than in refinery:

1. making sure versions are contiguous (we only check that the applied migrations have matching order)
2. comparing checksum, version/name should be enough

[serprex]

@iskakaushik is refinery-cli being used to manage customer migrations? if so, I can look to get this upstreamed

[serprex]

#926 passes after being rebased onto this PR

[serprex]

Spoke with Kaushik, rolling our own database migration code is too far into yak shaving, so will have to get this moved upstream