EE: User can create a group level cluster and install applications

See merge request gitlab-org/gitlab-ee!8080

Remove circular dependency on Redactable in migration

See merge request gitlab-org/gitlab-ee!8387

Gitlab::BackgroundMigration::RedactLinks was prepending
EE::Gitlab::BackgroundMigration::RedactLinks, while
EE::Gitlab::BackgroundMigration::RedactLinks was trying to include
Gitlab::BackgroundMigration::RedactLinks::Redactable. Ruby 2.5.3 failed
with an uninitialized constant
(https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/118388511).

However, we only need to raise for project_type clusters to maintain
previous behaviour.

In all probablity this requirement to have actual_namespace came from
KubernetesService and will no longer be required soon.

Use presenters instead otherwise we will have x2 overides in EE

Refacotr project or group specific `if` logic to be contained within
each presenter instead.

Also add :override to ensure super method exists.

Use model method as single source of truth instead of splitting between
presenter and Kubernetes model

Group clusters should not allow Project Namespace so don't show that
field input too

Currently cluster_health is only available for Project level clusters
because we haven't figured out how to install Prometheus for a Group of
projects.

Based on BE reviewer feedback

As the frontend is still in progress and other related backend is still
in prgress we need a feature flag to turn off Group Clusters.

These applications will need further work in future issues to enable
them to work with groups of projects.

Remove the requirement to have actual_namespace before using kubeclient.

- Add pages javascripts to intialize clusters for group pages

- Move specs asserting gcp specific validations from controller into
UpdateService spec

- Also teach Clusters::ApplicationController about groups

As this is the only item in this menu, make Kubernetes the link for the
sidebar item too.

- maintainer for group can read, create, update, and admin cluster
- project user, at any level, cannot do anything with group cluster

CE upstream - 2018-11-09 14:21 UTC

See merge request gitlab-org/gitlab-ee!8382

Add e2e test of push via HTTP via Git protocol v2

See merge request gitlab-org/gitlab-ce!22925

Fixing failure due to comment filters

Closes gitlab-org/quality/nightly#35

See merge request gitlab-org/gitlab-ee!8376