Repo files list: Lazy load visible batch of commits first

In !71633 (merged) we introduced a way to lazy load commits.

In order to support lazy loading in reverse (scrolling up), we load the batch above the currently visible batch.

As a further enhancement, we could load the currently visible batch before we load the batch above the currently visible batch.

This should be a fairly simple fix (simply swapping around the requests in commits_service.js#L62) and perhaps adding a test to check the order of the requests.