Creates an index in ci_stages before migrating pipeline stages from
ci_builds, to improve migration performance.

* master: (524 commits)
  Improve user experience around slash commands in instant comments
  Fix LFS timeouts when trying to save large files
  retryable? is now available for CommitStatus
  Resolve "Documentation of `.gitlab-ci.yml` states incorrect example for variables"
  Fix test failures
  Add slugify project path to CI enviroment variables
  Fixed typo: craeted -> created
  32118 Make New environment empty state btn lowercase
  Expose import_status in Projects API
  32832 Remove overflow from comment form for confidential issues and vertically aligns confidential issue icon
  Fix test failures
  Allow manual bypass of auto_sign_in_with_provider
  Fix keys seed
  Allow users to be hard-deleted from the API
  fixup some classnames and media queries
  Enable the Style/PreferredHashMethods cop
  Lint our factories creation in addition to their build
  Don’t schedule workers from inside transactions
  Allow scheduling from after_commit hooks
  Forbid Sidekiq scheduling in transactions
  ...

Conflicts:
	db/schema.rb
	spec/spec_helper.rb

Port fix-realtime-edited-text-for-issues 9-2-stable fix to master.

See merge request !11478

Add slugified project path to CI environment variables

Closes #31061

See merge request !11838

Initial implementation for real time job view

Closes #31397

See merge request !11651

Forbid Sidekiq scheduling in transactions

Closes #27233

See merge request !9376

ConvDev Index

Closes #30469

See merge request !11377

Improve user experience around slash commands in instant comments

Closes #32464

See merge request !11612

This makes it possible to test migration on the schema this migration
was written for, without a need to specify a previous schema version
manually.

Add `$CI_ENVIRONMENT_URL` as a job variable

Closes #25680

See merge request !11695

Fix LFS timeouts when trying to save large files

Closes #33218

See merge request !11866

The following was happening:

1. Workhorse stores an LFS file in /var/opt/gitlab/gitlab-rails/shared/lfs-objects
2. CarrierWave then renames the file to a temporary directory (e.g. /opt/gitlab/embedded/service/gitlab-rails/tmp)
3. CarrierWave then renames the file to its final location (e.g. /var/opt/gitlab/gitlab-rails/shared/lfs-objects)

When the LFS upload path was on a different filesystem than the Rails
installation, step 2 could take a longer than 10 seconds, at which point Workhorse
would time out with "badgateway: failed after 10s: context canceled".

This change makes the work path in the same root as the LFS storage path, preventing moves
across filesystems.

Closes #33218

Merge branch '32992-consider-using-zopfli-over-standard-gzip-compression-for-webpack-assets' into 'master'

Use zopfli for better asset compression and disable compression in CI

Closes #32992

See merge request !11798

Resolve "Documentation of `.gitlab-ci.yml` states incorrect example for variables"

Closes #30337

See merge request !11895

32118 Make New environment empty state btn lowercase

Closes #32118

See merge request !11350

Document go1.8.3 as dependency

See merge request !11245

Expose import_status in Projects API

Closes #19646

See merge request !11851

Allow manual bypass of auto_sign_in_with_provider

Closes #3786

See merge request !11884

32832 Remove overflow from comment form for confidential issues and vertically a…

Closes #32832 and #32926

See merge request !11867

Allow users to be hard-deleted from the API

See merge request !11853

Fixed typo: craeted -> created

See merge request !11886

Use the new Gitaly CommitDiff RPC

See merge request !11826