This change converts the old RB.DiffFragmentQueueView to TypeScript,

along with the DataUtils methods which it uses. This involves several

pieces:

Changed the queue to not inherit from a Backbone view. This doesn't

  actually do any view things, it's purely an orchestration class.
Renamed it to DiffFragmentQueue and moved into a utils/ directory.
Updated the DataUtils methods to return promises for their results,

  and marked the callback function parameters as deprecated.
Rewrote the fragment loading to use promises and async/await instead

  of $.funcQueue, and fetch instead of $.ajax.

Ran js-tests.
Opened a review request with a bunch of diff comments and saw all the

  diff comment fragments load correctly.
Opened the review dialog with a bunch of pending diff comments and saw

  all the diff comment fragments load correctly.
Expanded sections of the diff for the reviews and review dialogs.