feat(kubevirt): add patch get-applied-checksum

[yaroslavborbat]

Description

This patch introduces the GetAppliedChecksum() method in virt-launcher.

virt-handler now tracks synchronized VMIs and computes their checksums. Periodically, it queries virt-launcher for the applied checksum. This ensures that we have two checksums:

The last one sent for synchronization.
The one actually applied.
Storing these checksums in VMI annotations helps verify that spec changes were pushed by virt-handler and not by an attacker.

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

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.

Changelog entries

section:  feat
type: core
summary: virt-handler now tracks synchronized VMIs and computes their checksums. Periodically, it queries virt-launcher for the applied checksum. This ensures that we have two checksums: