fix(core): skip node placement migration during volume migration

[danilrwx]

Description

Prevent the workload updater from creating nodeplacement-update-* VMOPs while a KubeVirt VMI has an active volume migration state.

The node placement handler now skips automatic migration when VolumesChange=True or status.migratedVolumes is not empty.

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

During local disk migration, KubeVirt can temporarily set NodePlacementNotMatched=True because the running pod placement and the desired disk/node affinity differ while volumes are being switched.

Previously, the workload updater treated this transient state as a node placement change and created an extra nodeplacement-update-* operation for the same VM. This could interfere with disk migration and leave the VM/VMI in a stale volume migration state.

What is the expected result?

1. Start migration for a VM with a local disk.
2. While the VMI has VolumesChange=True or non-empty status.migratedVolumes, no nodeplacement-update-* VMOP is created.
3. Disk migration completes without an extra workload updater migration for the same VM.

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: fix
summary: Prevent node placement updates from interrupting active VM volume migration.
impact_level: low