Switch imported cluters to use new v1 management cluster

[eva-vashkevich]

Is your feature request related to a problem? Please describe.

There will be changes to v1 management cluster that we will need to acomodate
#50036

Describe the solution you'd like

Describe alternatives you've considered

Additional context

[moio]

Consider closing this issue or adapting its title/description as rancher/rancher#50036 is now closed in favor of rancher/rancher#53679

The design premise was to create a new cluster type, but now that idea is abandoned in favor of the rationalization of responsibilities across existing types, details in:

https://docs.google.com/document/d/1r9KG9DKGqZPxl9K1OqcJBYeNAFWUfGp93CmqXg8ZVs0/edit?tab=t.0#heading=h.nqwle44w55sr