Port of 1381-present-commits-pagination-headers-correctly to EE

See merge request !1357

Resolve "Squash commits fails for branches named HEAD"

Closes #1861

See merge request !1391

Port of 26202 change dropdown style slightly to EE

See merge request !1380

This would print an ambiguous refs warning, so silence that with
--quiet. HEAD in this context will refer to the 'current commit', not
the ref with that name.

Porting IssueBoardSorting feature from CE

See merge request !1388

Code improvements

See merge request !1385

Allow all parameters of group webhooks to be set through the UI

Closes #1853

See merge request !1376

Speed up MergeRequest::RefreshService spec by combining examples

See merge request !1386

Fix edit last visual token

See merge request !1383

Fix filtered search visual token editing dropdown

See merge request !1384

Add a GitLab Geo download scheduler for LFS files

See merge request !1382

Add filtered search visual tokens (ee)

See merge request !1378

The download scheduler works as follows:

1. Load a batch of IDs that we need to download from the primary (DB_RETRIEVE_BATCH) into a pending list.
2. Schedule them so that at most MAX_CONCURRENT_DOWNLOADS are running at once.
3. When a slot frees, schedule another download.
4. When we have drained the pending list, load another batch into memory, and schedule the remaining files, excluding ones in progress.
5. Quit when we have scheduled all downloads or exceeded an hour.

Basic support to track the backfilling of repositories

See merge request !1197

Export issues to CSV

Closes #1480

See merge request !1126