Add cross-cluster restore to KubeTaskWith{Backup,Restore}PVC

[anand-veeam]

Change Overview

Summary

Adds cross-cluster restore support to KubeTaskWith{Backup,Restore}PVC by
having the backup function emit the CSI snapshot handle and the restore
function reconstruct a bridge VolumeSnapshot + VolumeSnapshotContent on the
dest cluster when the original snapshot doesn't exist locally.

Pattern mirrors K10's CreatePVCandSnapshotFromSource
(kio/exec/internal/phaseutils/phaseutils.go:542): clone the dest
VolumeSnapshotClass with DeletionPolicy: Retain, CreateFromSource using
the clone, defer cleanup of the VS+VSC after the restore pod completes.
Kopia content is preserved because the cloned class carries Retain.

Changes

Backup side (KubeTaskWithBackupPVC)

• Emit snapshotHandle output by reading
  VolumeSnapshotContent.spec.source.snapshotHandle after the CSI snapshot
  reaches terminal state.
• Warn-log if the handle can't be read so cross-cluster failures are
  observable at backup time, not at restore time.

Restore side (KubeTaskWithRestorePVC)

• New optional snapshotHandle arg.
• Auto-fill volumeSnapshotName, snapshotHandle, restoreSize from the
  input artifact's KeyValue (K10 catalog convention) so the blueprint
  doesn't have to re-template them as args.
• New ensureRestoreSnapshot step before PVC provisioning:
  • VS exists on dest → noop (same-cluster behavior unchanged)
  • VS missing → clone source VSClass on dest with Retain, CreateFromSource
    using the kopia handle, defer VS+VSC cleanup at end of run().
• snapshotClassForRestore skips kanister-clone-* classes to avoid
  nested-clone loops on subsequent restores.

Please check the type of change your PR introduces:

• 🚧 Work in Progress
• 🌈 Refactoring (no functional changes, no api changes)
• 🐹 Trivial/Minor
• 🐛 Bugfix
• 🌻 Feature
• 🗺️ Documentation
• 🤖 Test
• 🏗️ Build

Issues

• fixes #issue-number

Test Plan

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

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