pkg/webhook: refactor Propagation Policy test

[mohamedawnallah]

Description

In this commit, we refactor propagation policy names and check on number of patches after the mutation happens.

Motivation and Context

Motivated by @XiShanYongYe-Chang's comment #5494 (comment).

What type of PR is this?

/kind cleanup

Which issue(s) this PR fixes:
Follow-up on #5492.

Does this PR introduce a user-facing change?:

NONE

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 33.86%. Comparing base (671372a) to head (368b4b1).
Report is 10 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5537      +/-   ##
==========================================
+ Coverage   33.71%   33.86%   +0.15%     
==========================================
  Files         643      643              
  Lines       44500    44509       +9     
==========================================
+ Hits        15001    15071      +70     
+ Misses      28357    28289      -68     
- Partials     1142     1149       +7     

Flag	Coverage Δ
unittests	33.86% <ø> (+0.15%)	⬆️

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[XiShanYongYe-Chang]

Thanks
/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: XiShanYongYe-Chang

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