And pass default value of feature flag from yaml

Update feature flag description

- Only includes a simple header for now. More UI elements
to be added in later MRs
- Add some safe programming checks to make sure
JS doesn't fail when running on development as a
stand-alone page.

- Fix issue with iframe not spanning whole height
- Make "Sign in" text fixed so it doesn't scroll with content
- Add font-size to important text to make it smaller and
consistent with GitLab in general

- Add global translations in Vue templates
- Add init code for GitLab UI to the Jira Connect entry point
- Add use of feature flags in the app
- Add CSS used by GitLab UI for Boostrap and utilities

- Add feature flag on the backend and pass to frontend
- Hide some elements which will be removed in the new UI

[DevOps Adoption] Daily updates - part 2

See merge request gitlab-org/gitlab!50416

Improve code readability in nuget search service

See merge request gitlab-org/gitlab!50667

Merge branch 'scalability/665-create-introductory-documentation-and-tutorial-about-stage-group-dashboards' into 'master'

Create introductory documentation and tutorial about Stage Group dashboards

See merge request gitlab-org/gitlab!50570

Fix lint issues

See merge request gitlab-org/gitlab!50677

Introduce dismissal reason for vulnerability feedback

See merge request gitlab-org/gitlab!50632

Stablize register spec

See merge request gitlab-org/gitlab!50675

Migrate to native window scrolling

See merge request gitlab-org/gitlab!43167

We can replace jquery.scrollTo.js with commonUtils scrollToElement or
native browser scrolling.

Quarantine flaky default branch name setting spec

See merge request gitlab-org/gitlab!50645

Fix project export audit log spec

See merge request gitlab-org/gitlab!50644

Add Packages::Debian::GetOrCreateIncomingService

See merge request gitlab-org/gitlab!50431

Minor API readme style updates

See merge request gitlab-org/gitlab!50670

[RUN ALL RSPEC] Deprecations job

See merge request gitlab-org/gitlab!49792

Update Cohorts page to improve style

See merge request gitlab-org/gitlab!50668

Fixes several style and wording items.

Incorporated several style updates to page.

Change CE to EE

See merge request gitlab-org/gitlab!50656

Additional style and wording updates from recent Install change

See merge request gitlab-org/gitlab!50620

Improve GraphQL style guide docs

See merge request gitlab-org/gitlab!50641

Remove tier badging from doc links on index page

See merge request gitlab-org/gitlab!50637

Configure sampler intervals via environment variables

See merge request gitlab-org/gitlab!50625

This is useful for development but also to more easily
change these values in production.

Update language re. docs for disabled FFs

See merge request gitlab-org/gitlab!47917