Remove Restic code path from PodVolumeRestore

[blackpiglet]

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Fixes #9468

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.30%. Comparing base (fc6361b) to head (cccb125).

Files with missing lines	Patch %	Lines
cmd/velero-restore-helper/velero-restore-helper.go	0.00%	1 Missing ⚠️
pkg/controller/pod_volume_restore_controller.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9732      +/-   ##
==========================================
+ Coverage   60.98%   61.30%   +0.32%     
==========================================
  Files         384      383       -1     
  Lines       36612    36386     -226     
==========================================
- Hits        22327    22306      -21     
+ Misses      12677    12474     -203     
+ Partials     1608     1606       -2     

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[kaovilai]

This might cause upgrade failure on our side.

https://github.com/operator-framework/operator-controller/blob/main/docs/concepts/crd-upgrade-safety.md

Have we considered adding another version of the CRD ie. v2?

https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definition-versioning/#specify-multiple-versions

We can then implement conversion webhook to immediately deprecate/remove older v1 CRD.
https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definition-versioning/#upgrade-existing-objects-to-a-new-stored-version

[kaovilai]

For V1, we can keep same enums but edit description like https://github.com/vmware-tanzu/velero/pull/9676/changes#diff-e710ccbdbd4149cab26deb6b55961c09fdf6ef984d8ebfe252a6e30c40e8a31f

[shubham-pampattiwar]

Thanks for putting this together, the restic code path cleanup is great to see.
One thing I wanted to flag: removing existing enum values (restic, "") from the CRD schemas is a breaking change per the https://github.com/operator-framework/operator-controller/blob/main/docs/concepts/crd-upgrade-safety.md policy. This would block upgrades for OLM-managed deployments, and existing CRs in etcd with those values would fail validation against the new schema.
Could we keep the enum as-is and instead add controller-level validation that rejects restic / "" at reconcile time (e.g., fail with "restic uploader is no longer supported, use kopia")? Same end result without the schema-level break.

+1 to @kaovilai's concern as well.

[sseago]

+1 to avoiding the breaking change to CRDs. Without version bumps, it's ok to add to enum values but not to remove them. Failing with a validation error when Restic is specified should be sufficient.