Expose VSC SourceVolumeMode 1.14

[msfrucht]

Thank you for contributing to Velero!

Cherry-pick of #8261 as requested for Velero 1.14.

Please add a summary of your change

Copies the VolumeSnapshotContent SourceVolumeMode during DataUpload. Recent versions of the snapshot-controller do not allow the field to be changed from "Filesystem" or "Block" to nil resulting in a failure to move the VolumeSnapshot into the local namespace.

This was found in Kubernetes 1.29/OpenShift 4.16

@shubham-pampattiwar identified the underlying source of the behavior changes to https://kubernetes.io/blog/2024/04/30/prevent-unauthorized-volume-mode-conversion-ga/ and shows up in external-provisioner v4.0.0 and external-snapshotter v7.0.0.

This field is typically nil to begin with in other environments which doesn't trigger this error.

Does your change fix a particular issue?

Fixes #(issue)
#8259

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file (make new-changelog) or comment /kind changelog-not-required on this PR.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.73%. Comparing base (4a86f28) to head (8f037f2).
Report is 2 commits behind head on release-1.14.

Additional details and impacted files

@@              Coverage Diff              @@
##           release-1.14    #8280   +/-   ##
=============================================
  Coverage         58.73%   58.73%           
=============================================
  Files               346      346           
  Lines             28840    28841    +1     
=============================================
+ Hits              16940    16941    +1     
  Misses            10471    10471           
  Partials           1429     1429           

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