feat(core): report why a resource is terminating

[eofff]

Description

Adds a Deleting condition to VirtualDisk, VirtualImage, ClusterVirtualImage and VirtualMachineBlockDeviceAttachment explaining why a resource is stuck in Terminating:

• DeletionBlockedByProtection — still attached to VirtualMachine(s) (listed in the message);
• CleanupPending — waiting for owned subresources (PVC, DataVolume, Pods, Service, Ingress, NetworkPolicy) to be removed.

CleanUp now returns a human-readable reason alongside requeue; shared condition/message/cleanup helpers live in service and common/vm to avoid duplication across the four controllers.

Why do we need it, and what problem does it solve?

A resource stuck in Terminating gave no hint about what blocked deletion — the user had to inspect finalizers and subresources by hand. The cause is now visible directly in status.conditions.

What is the expected result?

While terminating, the Deleting condition names the blocker: an attached VM (protection) or the subresource being cleaned up (cleanup pending), then the object is removed once cleanup finishes.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: core
type: feature
summary: Report why a VirtualDisk, VirtualImage, ClusterVirtualImage or VirtualMachineBlockDeviceAttachment is terminating via a Deleting condition.