[cherry-pick][main]Expose the VolumeHelper to third-party plugins.

[blackpiglet]

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Does your change fix a particular issue?

Fixes #7818

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

Attention: Patch coverage is 40.98361% with 36 lines in your changes missing coverage. Please review.

Project coverage is 58.84%. Comparing base (28d64c2) to head (c4ce6a3).

Files	Patch %	Lines
internal/resourcepolicies/resource_policies.go	3.70%	26 Missing ⚠️
pkg/backup/actions/csi/pvc_action.go	53.84%	4 Missing and 2 partials ⚠️
pkg/controller/backup_controller.go	50.00%	1 Missing and 1 partial ⚠️
.../plugin/utils/volumehelper/volume_policy_helper.go	88.23%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7969      +/-   ##
==========================================
+ Coverage   58.83%   58.84%   +0.01%     
==========================================
  Files         345      346       +1     
  Lines       28795    28844      +49     
==========================================
+ Hits        16941    16973      +32     
- Misses      10425    10440      +15     
- Partials     1429     1431       +2     

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