minor api enhancements

[Diaphteiros]

What this PR does / why we need it:

• Adds a WaitForClusterDeletion flag to the spec of ClusterRequest resources.
• Adds a list of resource types to the status of ServiceProvider resources.

Both changes are related to a discussion from today which revolved around the topic how we can best ensure that a v2 MCP resource is only deleted after all services depending on it have been removed too.

Which issue(s) this PR fixes:
Part of openmcp-project/backlog#210

Special notes for your reviewer:

Release note:

`ClusterRequest` resources can now be configured to delay the removal of their own finalizer (therefore also delaying their own deletion) until the corresponding `Cluster` is gone when the request is deleted, instead of the finalizer being removed immediately after the deletion of the Cluster has been triggered. Cluster providers need to take care to implement the feature accordingly. The `spec.waitForClusterDeletion` flag has no effect in situations where deletion of the `ClusterRequest` does not trigger a deletion of the corresponding `Cluster`.

`ServiceProvider` resources must now expose a list of their service resource types in their status. Service providers must take care to implement the feature accordingly. This serves as a kind of 'service catalog' that allows to look up the k8s resources that belong to a specific service provider.