Summary:
## Why?
1. RCTTurboModuleLookupDelegate sounds a bit nebulous.
2. In JS and Java, we use a `TurboModuleRegistry` interface to require TurboModules. So, this diff will make JS, Java, and ObjC consistent.
Changelog:
[Internal]
Reviewed By: PeteTheHeat
Differential Revision: D22405754
fbshipit-source-id: 30c85c246b39d198c5b8c6ca4432a3196ca0ebfd