Only some tabs support basic search and others need Elasticsearch

For https://gitlab.com/gitlab-org/gitlab/issues/33678 this will allow us
to roll out Elasticsearch more confidently as users can always revert
back if there is a problem with the Elasticsearch results.

Setting query param basic_search=true on any search now should not use
Elasticsearch. Introduce Search::Elasticsearchable to not duplicate the
logic of whether or not to use elasticsearch.

Enable frozen string for spec/routing

See merge request gitlab-org/gitlab!19274

Partially addresses:

https://gitlab.com/gitlab-org/gitlab/issues/27703

Update gems to support Rails 6

See merge request gitlab-org/gitlab!18969

This prepares us for the upgrade to Rails 6

Fix flaky DesignResolver spec.

Closes #35124

See merge request gitlab-org/gitlab!19262

Move all cluster create documentation to new page

Closes #30577

See merge request gitlab-org/gitlab!18233

- Also fixes links to old locations where neccessary.
- Put redirect in for an old location.

Add content that variables can be passed to pipelines/new page

See merge request gitlab-org/gitlab!18731

Quarantine delete group issue board spec

See merge request gitlab-org/gitlab!19227

Failure is transient and needs investigation
Issue: https://gitlab.com/gitlab-org/gitlab/issues/34936

Remove foreman gem

See merge request gitlab-org/gitlab!19200

There is no explicit order currently although one is being introduced in
https://gitlab.com/gitlab-org/gitlab/merge_requests/17788#note_230875678

`contains_exactly` is the correct way to test the resolver, as ordering
isn't important to the resolver itself.

https://gitlab.com/gitlab-org/gitlab/issues/35124

Fix spec for Resolvers::DesignManagement::DesignResolver

See merge request gitlab-org/gitlab!19260

Remove extra and

See merge request gitlab-org/gitlab!19239

Update doc/user/markdown.md, doc/user/img/gitlab_task_lists.png files

See merge request gitlab-org/gitlab!18844

Disable protected path throttling by default

Closes #34212

See merge request gitlab-org/gitlab!19185

Fix todos created by private group mentions

Closes #33902

See merge request gitlab-org/gitlab!19037

Add pages_domains#clean_certificate method

See merge request gitlab-org/gitlab!17487

Geo - Migrate LFS objects into their own registry table

See merge request gitlab-org/gitlab!18415

Part of https://gitlab.com/gitlab-org/gitlab/issues/10067

Hide Cloud Run on GKE behind a feature flag

See merge request gitlab-org/gitlab!19063

Currently creating a cluster using Cloud Run on
GKE results in a cluster that serverless
functions cannot be deployed to due to the issue
described in:
https://gitlab.com/gitlab-org/gitlabktl/issues/54

This hides the feature behind a feature flag until
that issue can be addressed in either gitlabktl or
upstream in the tm cli.

Enable frozen string for spec/requests

See merge request gitlab-org/gitlab!19143

Partially addresses:

https://gitlab.com/gitlab-org/gitlab/issues/27703

Update Advanced Search Syntax Docs

Closes #1086

See merge request gitlab-org/gitlab!19240

Provides information that only default branch is supported

It will be used in haml views to easily delete certificate
by clicking to one link