- Includes instance methods on Group model to detect when a group has
AutoDevOps explicitly/implicitly enabled/disabled.
- Includes migration to add a new column to namespaces table
- Add UI necessary modifications
- Add service and controller to update auto devops
related instances
- Updates project and groups auto devops badges

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52447

Currently if a project is inside a nested group and a user doesn't have
specific permissions for that group but does have permissions on a
parent group the `GET /projects/:id` API call will return the following
permissions:

```json
permissions: { project_access: null, group_access: null }
```

It could also happen that the group specific permissions are of lower
level than the ones the user has in parent groups. This patch makes it
so that the permission returned for `group_access` is the highest from
amongst the hierarchy, which is (ostensibly) the information that the
API user is interested in for that field.

It gathers list of file paths to delete before destroying
the parent object. Then after the parent_object is destroyed
these paths are scheduled for deletion asynchronously.

Carrierwave needed associated model for deleting upload file.
To avoid this requirement, simple Fog/File layer is used directly
for file deletion, this allows us to use just a simple list of paths.

With this MR, group clusters is now functional, so default to enabled.

Have a single setting on the root ancestor group to enabled or disable
group clusters feature as a whole

Even though we currently only should have one group for a cluster, we
allow the flexibility to associate to other groups in the future.

This also matches the runner <=> groups association.

- Adds Cluster#first_group, aliased to Cluster#group. For the
conceivable future, a cluster will have at most one group.

- Prevent mixing of group and project clusters. If project type
clusters, it should only have projects assigned.  Similarly with groups.

- Default cluster_type to :project_type. As it's very small table we can
set default and null: false in one release.