R1:6a2e27ba8d70

Put all DifferentialComment loading behind DifferentialCommentQuery

Summary:
Ref T2222.

I'm thinking about how I want to approach the Asana sync, and I want to try to do T2222 first so that we can build it cleanly on top of ApplicationTransactions. I think we can at least walk down this road a little bit and if it turns out to be scary we can take another approach.

I was generally very happy with how the auth migration turned out (seemingly, it was almost completely clean), and want to pursue a similar…