Remove expand diff to full file feature flag

See merge request gitlab-org/gitlab-ce!26614

Fix duplicated bottom match line

Closes #59147

See merge request gitlab-org/gitlab-ce!26402

(cherry picked from commit 7d3c5d88)

8723f292 Fix diff bottom expand button appears twice

Phil Hughes authored 6 years ago and Mark Chao committed 6 years ago

The user can also toggle between the diff changes and
the full file diff.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19054

- replaced file.too_large
- replaced file.text
- replaced file.collapsed

We don't need a series of attributes to render diff files on
discussions.json request. Therefore this MR removes lots of unnecessary
attributes from the request, mainly the highlighted diff lines, which
are pretty expensive.

Renders mode changed and renamed file merge request diff
viewers on the frontend.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52607

Partially addresses #47424.