- Set as uninstallable app
- Update docs
- Adjust specs

- This enables us to use a scope to query all clusters in group
hierarchy order in one query, and also enables us to union to instance
clusters later.

- Handle case where clusters not present at level. In which case the
query should go ahead and return the next level's clusters.

- Swap with new CTE query behind Feature flag. This FF is default
disabled.

- JupyterHub must not be available (installed or updated)

- enabled uninstallation
- give it a specific uninstall message
- ajust specs

Now we have terminals for instance and group clusters we can remove the
FF now. Deploying to instance clusters has been working without
complaints too.

Instance-level cluster pod terminal access

Closes #55489, #55488, #55487, and #61156

See merge request gitlab-org/gitlab-ce!28613

This enables terminals for group and project level clusters.
Previously there was no way to determine which project (and
therefore kubernetes namespace) to connect to, moving this
logic onto Environment means the assoicated project can be
used to look up the correct namespace.

Enable JIT Kubernetes resource creation for project level clusters

See merge request gitlab-org/gitlab-ce!29515