Added unit tests for resourceinterpreter webhook configmanager

[anujagrawal699]

Description:
This PR adds comprehensive unit tests for the resourceinterpreter webhook configmanager. These tests verify the core functionality of webhook configuration handling and access, including configuration syncing, merging, and accessor behaviors.

Additions:

1. pkg/resourceinterpreter/customized/webhook/configmanager/manager_test.go
2. pkg/resourceinterpreter/customized/webhook/configmanager/accessor_test.go

Test Coverage:

1. pkg/resourceinterpreter/customized/webhook/configmanager/manager_test.go : 0% to 81%
2. pkg/resourceinterpreter/customized/webhook/configmanager/accessor_test.go : 0% to 86.4%

What type of PR is this?
/kind feature

Which issue(s) this PR fixes:
Fixes a part of #5470

Does this PR introduce a user-facing change?:

NONE

[karmada-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.19%. Comparing base (ae65de4) to head (352446e).
Report is 4 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5832      +/-   ##
==========================================
+ Coverage   46.04%   46.19%   +0.14%     
==========================================
  Files         659      660       +1     
  Lines       53957    53985      +28     
==========================================
+ Hits        24847    24938      +91     
+ Misses      27494    27427      -67     
- Partials     1616     1620       +4     

Flag	Coverage Δ
unittests	46.19% <ø> (+0.14%)	⬆️

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---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[RainbowMango]

The #5834 will fix the failing tests. Please rebase this PR after #5834.
Sorry for the inconvenience.

[anujagrawal699]

The #5834 will fix the failing tests. Please rebase this PR after #5834. Sorry for the inconvenience.

Okay, Thanks!

[anujagrawal699]

/retest

[karmada-bot]

@anujagrawal699: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[anujagrawal699]

@anujagrawal699: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

Hi @XiShanYongYe-Chang , can u trigger a retest?

[XiShanYongYe-Chang]

Yes~
/retest

[zhzhuang-zju]

/assign