R1:8f9b9484471a

When showing a diff-of-diffs, hide files which didn't get any more changes and have no inlines

Summary:
Ref T13137. See that task for discussion.

When we show a diff-of-diffs, we often render stubs for files which didn't change between the diffs. These stubs usually aren't a big deal, but for certain types of changes (like refactors) they can create a lot of clutter.

Instead, hide these stubs and show a notice that we hid them.

Test Plan:
- Created a revision affecting 4 files.
- Updated it with a…