Gitaly mirroring migration prep

Closes gitaly#816

See merge request gitlab-org/gitlab-ce!15775

Backport epic in issue

See merge request gitlab-org/gitlab-ce!15799

fixes some markup issues in the js style guide docs

See merge request gitlab-org/gitlab-ce!15828

Moved URL utility methods into exported es modules

See merge request gitlab-org/gitlab-ce!15783

Animate contextual sidebar; change class names for easier readability

Closes #35724

See merge request gitlab-org/gitlab-ce!15797

Docs: add index for `doc/administration/operations/`

See merge request gitlab-org/gitlab-ce!15852

Add cop for use of remove_column

See merge request gitlab-org/gitlab-ce!15855

small change to make less conflict with EE version

See merge request gitlab-org/gitlab-ce!15809

remove_column should only be used in the up (or change) step of a migration if
it's a post-deployment migration. Otherwise there will be downtime due to the
ActiveRecord column cache, which we can avoid by using the IgnorableColumn
concern in combination with a post-deployment migration.

Resolve merge conflicts with dev.gitlab.org/master after security release

See merge request gitlab-org/gitlab-ce!15851

Remove allocation tracking code from InfluxDB sampler for performance

Closes gitlab-com/infrastructure#3250

See merge request gitlab-org/gitlab-ce!15834

Remove issues.assignee_id column

Closes #30453

See merge request gitlab-org/gitlab-ce!11637

Bugfix: User can't change the access level of an access requester

Closes #40743

See merge request gitlab-org/gitlab-ce!15832

Properly bump prometheus-client-mmap gem versions

See merge request gitlab-org/gitlab-ce!15825

The endpoint was returning 404 because it was only searching on the
current members of a Group or Project and not the access requesters.

This migration also needs to be a post-deployment migration, as it removes a
column.

Remove a header level in the new 'Automatic CE->EE merge' doc

See merge request gitlab-org/gitlab-ce!15843

Keep track of the circuit breaker access check timings

Closes #39698

See merge request gitlab-org/gitlab-ce!15612

Do not raise when downstream pipeline is created

Closes #40987

See merge request gitlab-org/gitlab-ce!15837

Pick 10.2.4 security fixes into master

See merge request gitlab-org/gitlab-ce!15821

# Conflicts:
#   app/assets/javascripts/issue_show/components/app.vue

Signed-off-by: NRémy Coutable <remy@rymai.me>

Add recaptcha_check_if_spammable for issualbes than arent spammables

See merge request gitlab-org/gitlab-ce!15817

Using update_column_in_batches means that we can chunk the updates.

Todo count calculations now expired quicker for top bar stats

See merge request gitlab-org/gitlab-ce!15794

Turn" push a file" into a scenario

See merge request gitlab-org/gitlab-ce!15617

Fix image view mode

Closes #40945

See merge request gitlab-org/gitlab-ce!15803

Convert Compare and CompareAutocomplete classes into ES module syntax

See merge request gitlab-org/gitlab-ce!14857

Fix gitlab:import:repos Rake task moving repositories into the wrong location

Closes #40765

See merge request gitlab-org/gitlab-ce!15823