refactor(vmsnapshot): remove freeze/unfreeze logic from VMSnapshot controller

[hardcoretime]

Description

Removes filesystem freeze/unfreeze logic from VMSnapshot controller. The VMSnapshot controller was incorrectly handling freeze/unfreeze operations, which is the responsibility of VDSnapshot.

Changes made:

• Removed freezeVirtualMachine(), unfreezeVirtualMachineIfCan(), and needToFreeze() methods from VMSnapshot lifecycle handler
• Removed all freeze/unfreeze related code from the Handle() function
• Simplified Snapshotter interface from 13 to 6 methods (removed: Freeze, Unfreeze, IsFrozen, CanFreeze, CanUnfreezeWithVirtualMachineSnapshot, SyncFSFreezeRequest, GetVirtualMachineInstance)
• Updated unit tests to remove mock fields and tests related to freeze/unfreeze
• Regenerated mock to match new interface

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

The VMSnapshot controller was duplicating freeze/unfreeze logic that already exists in VDSnapshot controller. This caused:

1. Race conditions - both controllers could attempt to freeze/unfreeze the same VM
2. Code duplication - same logic implemented in two places
3. Violation of Single Responsibility Principle - VMSnapshot should only coordinate VDSnapshot creation

VDSnapshot is the correct place for freeze/unfreeze because:

• VDSnapshot is created for each disk of the VM
• VDSnapshot already has proper coordination logic via CanUnfreezeWithVirtualDiskSnapshot
• VDSnapshot handles cleanup (unfreeze) on deletion via DeletionHandler

What is the expected result?

• VMSnapshot now only creates VDSnapshot resources and waits for them to become Ready
• VDSnapshot is fully responsible for filesystem freeze/unfreeze operations
• No duplicate freeze/unfreeze attempts
• Cleaner separation of concerns

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: vmsnapshot
type: chore
summary: "Remove freeze/unfreeze duplication from VMSnapshot controller. VDSnapshot is now fully responsible for filesystem freeze/unfreeze operations."
impact_level: low