fix(vm): create a kvvm with an optional cpu feature invtsc

[yaroslavborbat]

Description

Use "optional" policy for "invtsc" cpu feature.

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

The problem with invtsc feature occurs when vmclass "Discovery" is used or feature is specified explicitly.

When "required" policy set for "invtcs" feature, kubevirt adds nodeSelector to schedule VM to the node with the lowest tsc frequency. This nodeSelector ignores other rules and not what user expects. This PR changes policy to "optional" to respect other rules in the nodeSelector.

Example of the label in the nodeSelector:

scheduling.node.virtualization.deckhouse.io/tsc-frequency-3407964000: "true"

What is the expected result?

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.