feat(vmbda): forbid hotplug of RWO disks during migration

[loktev-d]

Description

Forbids hot-plugging a ReadWriteOnce disk into a virtual machine while it is migrating.

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

A ReadWriteOnce volume can only be attached on a single node. Hotplugging one during a live migration pins its PVC to a node and breaks scheduling of the migration target. This change prevents that class of failure by refusing to start an RWO hotplug while the VM is migrating; the attachment simply waits and proceeds automatically once migration completes.

What is the expected result?

With a VM running and an RWO VirtualDisk available (not attached):

1. Start a live migration of the VM.
2. While it is migrating, create a VirtualMachineBlockDeviceAttachment for the RWO disk.
3. The VMBDA stays in Pending with Attached=False / reason BlockedByMigration ("Cannot hotplug a ReadWriteOnce disk while the virtual machine is migrating.")
4. When the migration completes, the VMBDA is re-reconciled and transitions to Attached.

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: vmbda
type: feature
summary: forbid hotplug of RWO disks during migration

[deckhouse-BOaTswain]

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