R1:12b53e003b22

Add a UI for reviewing database schemata

Summary:
Ref T1191. Plan here is:

- Build a tool showing the current schemata status (this diff).
- Have it compare the current status to the desired status (partly here, mostly in future diffs).
- Then add a migration tool, and eventually a setup issue to tell people to run it.

Test Plan:
Reviewed current schemata.

{F204492}

{F204493}

{F204494}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential…