Make Kubernetes service templates readonly

See merge request gitlab-org/gitlab-ce!29044

We are deprecating this service in favor of instance wide clusters.
Therefore we removed some code that is not anymore needed for a
readonly cluster and also we added some flags to allow for this
deprecation. These flags are to be removed in the next release when
we finally completelly remove KubernetesService.

Migrate Kubernetes service integration templates to clusters

See merge request gitlab-org/gitlab-ce!28534

Updated docs for Merge Trains

See merge request gitlab-org/gitlab-ce!29771

Don't use Kubernetes namespaces with no token

See merge request gitlab-org/gitlab-ce!29643

Add index on invite-email to members

See merge request gitlab-org/gitlab-ce!29768

CE port of "Add test for git http operations for SSO enforced SAML group"

See merge request gitlab-org/gitlab-ce!29550

[CE] Validate page after visit in block

See merge request gitlab-org/gitlab-ce!29524

Expose currently supported events properly on services API

Closes #56737

See merge request gitlab-org/gitlab-ce!29736

Refresh service_account_token for kubernetes_namespaces

See merge request gitlab-org/gitlab-ce!29657

note that todos are not affected by GitLab Notification Email settings

See merge request gitlab-org/gitlab-ce!29539

Hashed Storage is enabled by default on new installations

See merge request gitlab-org/gitlab-ce!29586

Toolbar backport changes for CE

See merge request gitlab-org/gitlab-ce!29758

Merge branch 'ce-backport-11435-mr-search-by-approvers-doesn-t-use-reserved-values-for-none-and-any' into 'master'

Backport fix MR search by approvers

See merge request gitlab-org/gitlab-ce!29621

Backport docs for "Automatically index wikis in elasticsearch"

See merge request gitlab-org/gitlab-ce!29612

Move Dropdown to Stick to MR View App Button

Closes gitlab-ee#12184

See merge request gitlab-org/gitlab-ce!29767

updated documentation for Geo

Visual Review Toolbar Docs

See merge request gitlab-org/gitlab-ce!29641

The dropdown of changed pages in the review app should be attached to
the view app button. This moves it to the correct place. The Review App
button is to the right of both of those.

Disable hooks by setting an ENV var

See merge request gitlab-org/gitlab-ce!29672

Add collapsible sections to job log

See merge request gitlab-org/gitlab-ce!28642

Remove no longer valid password

See merge request gitlab-org/gitlab-ce!29751

Backport the EE schema to CE

Closes gitlab-ee#9686

See merge request gitlab-org/gitlab-ce!26940

CE backport for gitlab-org/gitlab-ee!14064: Add merge train position indicator

See merge request gitlab-org/gitlab-ce!29561

read_repository scope can be used for API

See merge request gitlab-org/gitlab-ce!29663

CE port of IP address restriction for groups

See merge request gitlab-org/gitlab-ce!29467

Fix list rendering on docs site

See merge request gitlab-org/gitlab-ce!29738

One can not upgrade straigt from 9.3 to 12.0, due to the schema changes
being backported. Instead, one must first upgrade to 11.11.X. Omnibus
already enforces this, and our online upgrade guidelines also cover
this.

By changing the CI config we don't have to adjust the backport migration
to handle a migration path that one can not take.