Issue 7068: add a finalizer to protect retained VSC

[Lyndon-Li]

Fix issue #7068, due to a behavior of CSI external snapshotter, manipulations of VS and VSC may not be handled in the same order inside external snapshotter as the API is called. So add a protection finalizer to ensure the order

[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (a036e8d) 60.58% compared to head (25fc2f4) 60.61%.

Files	Patch %	Lines
pkg/util/csi/volume_snapshot.go	79.06%	6 Missing and 3 partials ⚠️
pkg/exposer/csi_snapshot.go	50.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.12    #7114      +/-   ##
================================================
+ Coverage         60.58%   60.61%   +0.03%     
================================================
  Files               247      247              
  Lines             26499    26527      +28     
================================================
+ Hits              16054    16079      +25     
- Misses             9319     9321       +2     
- Partials           1126     1127       +1     

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