R1:31b6f69ff7c2

Allow CelerityResourceResponse to hold resources from multiple maps

Summary:
Ref T4222. Currently, CelerityResourceResponse holds response resources in flat maps. Instead, specify which map resources appear in.

Also, provide `requireResource()` and `initBehavior()` APIs on the Controller and View base classes. These provide a cleaner abstraction over `require_celerity_resource()` and `Javelin::initBehavior()`, but are otherwise the same. Move a few callsites over.

Test Plan:
- Reloaded pages.