R1:1e17fd31a4f9

Modernize Conpherence access to user preferences

Summary:
Ref T4103. Conpherence is doing some weird stuff and has its own redudnant settings object.

- Get rid of `ConpherenceSettings`.
- Use `getUserSetting()` instead of `loadPreferences()`.
- When applying transactions, add a new mechanism to efficiently prefill caches (this will still work anyway, but it's slower if we don't bulk-fetch).

Test Plan:
- Changed global Conpherence setting.
- Created a new Conpherence, saw setting set to global…