R1:a5ce56aa76e1

Allow `bin/storage adjust` to make key changes

Summary:
Ref T1191. These are a bit tricky because keys can interact with column changes, so basically we do three phases:

1. Nuke all bad keys.
2. Make all column (and database/table) changes.
3. Fix all nuked keys.

Test Plan: Ran migration locally. See note for remaining issues.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10599