CloneSet supports to reuse PVC during upgrade

[FillZpp]

Ⅰ. Describe what this PR does

CloneSet supports to reuse PVC during upgrade.

Newly added:

• CloneSetPVCReuseDuringUpdate feature-gate that enables CloneSet to reuse PVC during update.
• apps.kruise.io/keep-pvc-for-deletion label that can either be used by the above feature, or user can directly set it in pod or pod template, so that CloneSet will keep the PVC to reuse when it deletes the pod.

Ⅱ. Does this pull request fix one issue?

fixes #1876

[codecov]

Codecov Report

Attention: Patch coverage is 64.28571% with 5 lines in your changes missing coverage. Please review.

Project coverage is 50.93%. Comparing base (0d0031a) to head (e5011c4).
Report is 148 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/controller/cloneset/sync/cloneset_scale.go	0.00%	1 Missing and 1 partial ⚠️
pkg/util/specifieddelete/specified_delete.go	80.00%	2 Missing ⚠️
pkg/controller/cloneset/sync/cloneset_update.go	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1881      +/-   ##
==========================================
+ Coverage   47.91%   50.93%   +3.02%     
==========================================
  Files         162      193      +31     
  Lines       23491    24979    +1488     
==========================================
+ Hits        11256    12724    +1468     
+ Misses      11014    10949      -65     
- Partials     1221     1306      +85     

Flag	Coverage Δ
unittests	50.93% <64.28%> (+3.02%)	⬆️

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[furykerry]

is it necessary to introduce an extra label ? can we just checking the following logic?
!cs.Spec.ScaleStrategy.DisablePVCReuse && utilfeature.DefaultFeatureGate.Enabled(features.CloneSetPVCReuseDuringUpdate)

[kruise-bot]

@FillZpp: PR needs rebase.

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