Let ghostly inlines automatically expand changesets in enormous diffs

Summary:
Ref T7447. Ref T7870. When a diff affects more than 100 files, we collapse files by default, then expand files with inlines.

Ghostly inlines currently don't cause files to expand, but reasonably should.

Test Plan:
Before:

After:

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: yelirekim, epriestley

Maniphest Tasks: T7447, T7870

Differential Revision: https://secure.phabricator.com/D12495