Support pushing of feature flags to the frontend

Closes gitlab-org/release/framework#17

See merge request gitlab-org/gitlab-ce!22197

Adds `.json` to the end of pipelines endpoint

Closes #52472

See merge request gitlab-org/gitlab-ce!22293

Stuck block URL links to runners settings

Closes #52519

See merge request gitlab-org/gitlab-ce!22286

This adds a method to Gitlab::GonHelper called
`push_frontend_feature_flag`. This method can be used to easily expose
the state of a feature flag to Javascript code. For example, using this
method we may write the following controller code:

    before_action do
      push_frontend_feature_flag(:vim_bindings)
    end

    def index
      # ...
    end

    def edit
      # ...
    end

In Javascript we can then check the state of the flag as follows:

    if ( gon.features.vimBindings ) {
      // ...
    }

Fixes https://gitlab.com/gitlab-org/release/framework/issues/17

Enable even more frozen string in lib/**/*.rb

See merge request gitlab-org/gitlab-ce!22206

Feature improved branch filter sorting

See merge request gitlab-org/gitlab-ce!22166

Instance SAML SSO e2e test

Closes gitlab-qa#257

See merge request gitlab-org/gitlab-ce!22271

Add new sort option "most_stars" to "Group > Children" pages

See merge request gitlab-org/gitlab-ce!22121

When the job page is rendered we fetch the pipeline
endpoint to render the stages in the sidebar.
Without `.json` the response is cached, and when the
user goes back to the pipeline's page it renders the
json output instead of the Vue app

Removes link to deprecated project

See merge request gitlab-org/gitlab-ce!22281

docs: match where statements at in omnibus section

See merge request gitlab-org/gitlab-ce!22214

Avoid conflicting anchor name in documentation

See merge request gitlab-org/gitlab-ce!22213

Update GitLab Shell to v8.4.0 for new Gitaly auth scheme

Closes gitaly#1319

See merge request gitlab-org/gitlab-ce!22270

QA: Add test of adding a member to a project

See merge request gitlab-org/gitlab-ce!21753

Use ACCEPT_INSECURE_CERTS env var and fix step

Simplify saml signin

Fix rubo cop offence

Add missing # frozen_string_literal: true

- Also fixes minor style issues.

Documentation for delayed jobs

Closes #52127

See merge request gitlab-org/gitlab-ce!22117

Add Filesystem Performance Benchmarking documentation

See merge request gitlab-org/gitlab-ce!22202

Revert GitLab Pages version to v1.1.0

See merge request gitlab-org/gitlab-ce!22277

This works around the problem with domains not working
due to https://gitlab.com/gitlab-org/gitlab-pages/issues/170.

Adds a new QA test and the required page objects and related changes

Filesystem performance can have a big impact on overall GitLab
performance, especially for actions that read or write Git
repositories. This information will help benchmark filesystem
performance against known good and bad real-world systems.

Prettify all the things (part 5)

See merge request gitlab-org/gitlab-ce!22255

Prettify all the things (part 2)

See merge request gitlab-org/gitlab-ce!22250

Merge branch '52103-dropzone-css-is-failing-to-load-on-rspec-dev-and-staging-11-4-0-rc' into 'master'

Resolve "Dropzone css is failing to load on rspec, dev and staging 11.4.0 RC"

Closes #52103

See merge request gitlab-org/gitlab-ce!22272

Convert remaining issue board components into ES module syntax

See merge request gitlab-org/gitlab-ce!22210

QA: Retry registration before failing

See merge request gitlab-org/gitlab-ce!22033

[QA] Fix a wrong constant name

Closes gitlab-org/quality/nightly#22

See merge request gitlab-org/gitlab-ce!22264

Add allowance to merge feature flags MRs

See merge request gitlab-org/gitlab-ce!22267

Add `TOP_UPSTREAM_SOURCE_SHA` in `scripts/trigger-build`

See merge request gitlab-org/gitlab-ce!22260

Enhance and test JSON schema for deployments

See merge request gitlab-org/gitlab-ce!22266

Registration intermittently fails without an obvious cause.
The action to click the button seems to move focus to the right button
but nothing happens.
This change attempts to retry the action under the assumption that
Capybara or Chrome is misbehaving.
It also updates the selectors for the sign up page.