pkg/webhook: refactor Multi-Cluster Service test

[mohamedawnallah]

Description

In this commit, we refactor the multi-cluster service object names and check on number of patches after the mutation happens.

Motivation and Context

Motivated by @XiShanYongYe-Chang's comment https://github.com/karmada-io/karmada/pull/5494#discussion_r1758148145.

What type of PR is this?

/kind cleanup

Which issue(s) this PR fixes: Follow-up on #5517.

Does this PR introduce a user-facing change?:

NONE

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 48.16%. Comparing base (87ee756) to head (1467cea). Report is 2 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5539      +/-   ##
==========================================
+ Coverage   48.13%   48.16%   +0.02%     
==========================================
  Files         677      677              
  Lines       56068    56067       -1     
==========================================
+ Hits        26991    27002      +11     
+ Misses      27305    27296       -9     
+ Partials     1772     1769       -3     

Flag	Coverage Δ
unittests	48.16% <ø> (+0.02%)	:arrow_up:

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[mohamedawnallah]

I think this PR is now ready for review after rebasing on the master branch. Thanks!

cc: @XiShanYongYe-Chang

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[APPROVALNOTIFIER] This PR is APPROVED

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

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