Adapt clusterctl move to the new multi-tenancy model #3042
Description
User Story
As a User, I would like to use clusterctl for creating multy-tenant clusters.
Detailed Description
kubernetes-sigs/cluster-api-provider-aws#1713 is introducing the possibility for a provider to use many credentials with a single instance of a provider.
We should define if/how this scenario is supported by clusterctl.
Anything else you would like to add:
clusterctl already support two other different types of multy-tenancy, see https://cluster-api.sigs.k8s.io/clusterctl/commands/init.html#multi-tenancy
The approach introduced by CAPA is potentially by far simpler than the existing ones, and if we can potentially have all the providers to converge on the same approach this can result in a relevant simplification of manifests generation (e.g. no more need of the WebHook namespace) and of clusterctl (lots of corner cases won't be necessary anymore)
/kind feature