As we've defined how our JS codebase is going to work going forward, we've not been terribly disciplined about how we do imports. This change makes everything consistent with three import groups (3rd party, other modules, and the current module) that kind of matches the way that our Python code works. Where we can, this has been simplified to import everything from the top-level indexes, which makes sorting things alphabetically by module name much easier. Testing Done: Ran js-tests.