add toggle to override Approvals per-MR

Closes #582

See merge request !2016

Overview and use cases for repo limit

See merge request !2365

CE upstream: Friday

See merge request !2376

Enable service desk by default

Closes #2138

See merge request !2358

Add a license check on multiple issue boards

Closes #2567

See merge request !2317

Add new doc to Burndown Charts + use cases

See merge request !2364

Overview and use cases for Service Desk

See merge request !2337

Add overview and use cases for MR-related docs

See merge request !2350

Only show LDAP sync in progress flash banner on first login

See merge request !2322

We only overwrite `can_create_board?` so it allows creating multiple
boards when available.

And show a mention to the users so they know their boards didn't
disappear.

The `app/controllers/projects/boards_controller.rb` is identical to
the CE version by doing this.

I've split up the `spec/controllers/projects/boards_spec.rb` into the
logic that is on CE en what is on EE. However, they have diverged. So
they are likely (however less than before) to cause conflicts in the
future.

We'd need to move the EE specific spec logic for
`Projects::BoardsController#index` & `Projects::BoardsController#show`
into `spec/controllers/ee/projects/boards_controller.rb` however, some
of the tests in EE have been improved, so those improvements would
need to be ported to CE.

* upstream/master:
  Extend MR tabs a bit to cover up the avatar holder and collapse icon on scroll
  Update VERSION to 9.4.0-pre.
  Add CHANGELOG
  Fix some N+1 queries in the GET /projects API
  Don't show auxiliary blob viewer for README when there is no wiki
  Improve & fix the performance bar UI and behavior
  Remove orphaned haml files
  Fixed CHANGELOG.md for 9.3.4 release
  Add table for merge request commits
  34727 Remove two columned layout from project member settings
  Just draw :legacy_builds
  Upgrade GitLab Workhorse to v2.3.0
  Added test for the chart legend
  Use correct field for label name, fix default for unit to be blank
  Fix shorter route helpers in production environment
  Upgrade GitLab Pages to v0.5.0
  Banzai: Add tooltip attributes to reference filter.

Update VERSION to 9.4.0-pre.

See merge request !12702

CE upstream: Thursday

See merge request !2361

Add optional sha parameter when approving an MR through the API

Closes #2394

See merge request !2370

Extend MR tabs a bit to cover up the avatar holder and collapse icon on scroll

Closes #34153

See merge request !12589

Fix creation of push rules via POST API

Closes #2820

See merge request !2367

Don't show auxiliary blob viewer for README when there is no wiki

Closes #34732

See merge request !12689

Split docs for canary deployments and add use cases

See merge request !2359

Refactor push rules docs

See merge request !2362

Add use cases for Deploy Boards

See merge request !2357