chore(ci): check migration with ht optional on qemu 9.2.2

[nevermarine]

Description

Add HT CPU feature handling for VM class CPU model selection and keep HT optional for this variant.

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

PR #2378 introduced the same migration check with HT handling, but this branch keeps HT optional instead of required. This allows us to compare behavior against the required-HT version while preserving compatibility for environments where HT may be unavailable during migration checks.

What is the expected result?

1. Create or use a VMClass with CPU type model, discovery, or features.
2. Build the KubeVirt VM through the kvbuilder.
3. Verify the resulting CPU definition includes the ht feature.
4. Confirm the ht feature is added with optional policy when it is absent in the VMClass status.
5. Confirm existing ht entries are preserved and not duplicated.

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: ci
type: chore
summary: Add a QEMU 9.2.2 migration check variant with optional HT CPU feature handling.
impact_level: low