Extend kernel to support multiple subclusters

[sirtimid]

Allow users to create, retrieve, update and delete multiple subclusters, each with their own configuration. Currently the kernel only supports a single subcluster at a time. This enhancement will enable users to manage multiple independent vat subclusters and update the control panel UI to support viewing and managing these subclusters through the interface.

[rekmarks]

We're tabling this for now and may pick it up in the future.