Show private subgroups if member of parent group

Closes #32135

See merge request !11764

Rename "Slash commands" to "Quick actions"

Closes #27070

See merge request !11811

Create a post-deployment migration to update all existing notification settings
with at least one custom level enabled to the new format. Also handle the same
conversion when updating settings, to catch any stragglers.

Add columns for each custom notification level, defaulting to null. Read from
those columns if non-null, otherwise fall back to the serialized column. Writing
will write to the new column if `events` isn't manually set.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/27070

Deprecate "chat commands" in favor of "slash commands"

We looked for things like:

 - `slash commmand`
 - `slash_command`
 - `slash-command`
 - `SlashCommand`

When a user is authorized to a group, they are also authorized to see all the
ancestor groups and descendant groups.

When a user is authorized to a project, they are authorized to see all the
ancestor groups too.

Closes #32135

See merge request !11764

* upstream/master: (34 commits)
  Revert "Merge branch 'karma-headless-chrome' into 'master'"
  Make small pipeline schedules UI enhancements.
  Remove js classes from vue component that are not needed in vue component
  Update tests and application
  Adds "Pipeline" to job's sidebar
  Change border color of job's scroll controllers to $border-color
  Add database helpers 'add_timestamps_with_timezone' and 'timestamps_with_timezone'
  Added Tectonic to the page.
  Always check read_issue permissions when loading issue
  Handle legacy jobs without name
  Do not expose internal artifacts hash in build entity
  Use wait_for_requests instead of sleep 0.3
  Limit wiki container width
  Fix migrations testing support RSpec hooks order
  Rename BuildEntity to JobEntity
  Fix support for external_url for commit statuses
  Allow to access pipelines even if they are disabled, but only present jobs and commit statuses without giving ability to access them
  add CHANGELOG.md entry for !12036
  remove phantomjs-specific test hacks
  update karma job to use chrome build image created by gitlab-build-images!41
  ...

* upstream/master: (460 commits)
  Center dropdown for pipeline's  mini graph
  Documentation bugfix of invalid JSON payload example of Create a commit with multiple files and actions
  Fix filename method of GitlabUploader to return always real filename
  Ignore CVE-2017-5029 in Nokogiri
  Refactor atom builder by using xml.atom layout
  Let PhantomJS load local images
  Add a changelog entry
  Only add a description change note when no tasks are updated
  Doc: Add the need to upgrade to Go 1.8.3 in the 9.1->9.2 documentation as the upgrade fails with Go 1.5 (installed with Gitlab 8.1)
  Use gitaly 0.11.2
  Add the ability to perform background migrations
  Always render warnings icon in orange
  Fix a few translation for zh_TW
  Improve Job detail view to make it refreshed in real-time instead of reloading
  Attempts to run RSpec tests twice (1 retry)
  ignore name validation on importing
  Only show hover state on links and buttons
  Use vue files for navigation tabs and buttons
  doc: add example of scheduler when
  Add test for u2f helper and changelog entry
  ...