Allow admin users to view and manage all workspaces

### What feature do you want to see added?

Allow admin users to view and manage all workspaces.

### Why do you want this feature? Does it solve a problem?

This would allow admin users to have oversight of all workspaces in the platform.

### How should the feature be implemented?

It should reuse the existing layouts and views as much as possible, but be clear to the user that they're viewing someone else's workspace.

A separate screen should be used for viewing all workspaces, as opposed to just viewing the ones they can access.

### Additional context (if applicable)

This follows on from #128.

Start by reviewing issue #128 and the existing workspace layouts and views. Define the separate all-workspaces screen so administrators can view and manage every workspace while clearly seeing when they are viewing someone else's workspace.

Written by the indexing model from the issue text.