test(vm): port VM placement scenarios to new framework

[danilrwx]

Description

Port the remaining VirtualMachineAffinityAndToleration legacy scenarios to the new e2e framework under test/e2e/vm.

The PR now covers all placement-related checks from the former legacy suite:

• affinity / anti-affinity placement checks via status.nodeName
• migration after affinity updates
• spec.nodeSelector behavior
• spec.affinity.nodeAffinity behavior

The new tests use the modern framework helpers and object builders, add cluster prerequisite checks for required node topology, and keep migration verification based on fresh MigrationState data and resulting status.nodeName.

The PR also includes a follow-up fix for the migrated placement scenarios: the selected target node is now preserved across By(...) steps, so the final assertions validate the actual migration destination instead of an empty outer-scope value.

The obsolete legacy file was removed after the remaining scenarios were ported.

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

The old legacy affinity/toleration suite had already been partially migrated, but two placement scenarios still existed only in test/e2e/legacy/affinity_toleration.go.

Keeping the coverage split between legacy and the new framework made the suite harder to maintain and left outdated test infrastructure in place. This PR completes the migration, consolidates the scenarios in the new framework, and removes the leftover legacy implementation.

During validation, a scoping bug was also found in the new placement checks: targetNode was shadowed inside a step, which caused the outer variable to remain empty and made the final assertion fail despite successful migration. The fix makes the assertions stable and aligned with the actual migrated node.

What is the expected result?

1. Run the e2e suite that includes test/e2e/vm/affinity_toleration.go.
2. Verify that VM placement checks are performed through status.nodeName in the new framework.
3. Verify that changing spec.nodeSelector to the current node does not trigger migration.
4. Verify that changing spec.nodeSelector to another ready worker node triggers migration and updates status.nodeName.
5. Verify that changing spec.affinity.nodeAffinity to the current node does not trigger migration.
6. Verify that changing spec.affinity.nodeAffinity to another ready worker node triggers migration and updates status.nodeName.
7. Verify that final assertions use the real target node selected during migration.
8. Verify that the legacy test file is no longer needed.

Additionally, a compile-level validation was executed:

• cd test/e2e && go test ./... -run '^$'

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: test
type: chore
summary: "Fix VM placement e2e coverage by migrating remaining legacy scenarios and preserving selected target nodes in final assertions."
impact_level: low