Integrate multicluster POC frontend changes

Integrate the frontend changes from the multicluster POC, stories CONSOLE-2748 and CONSOLE-2767. The console should function as before if ACM is not installed. The cluster list should only become active when the backend is configured for multicluster. We should align the cluster picker with the latest designs.

This depends on CONSOLE-2832.

We should fix the known issues around access reviews and user settings.

Acceptance Criteria

• User settings are always read and set from the hub cluster rather than the spokes. The console service account only has authority to write the config map to the hub cluster.
• The cluster name is included in the cache key for self subject access reviews. There is a known bug in the POC where you can use an incorrect cached value after switching clusters that must be fixed.
• The code from the POC is cleaned up and merged, but inert if ACM is not installed.
• ACM is removed from the perspective switcher. The "All clusters" item in the cluster picker redirects to ACM.