Added second part of unit tests for pkg/detector

[anujagrawal699]

Description:
This PR significantly enhances the unit tests for the detector package. The improvements aim to increase code reliability, maintainability, and test coverage for various detector functions.

Modifications:

1. pkg/detector/detector_test.go

Key Improvements:

1. Implemented tests for ClaimPolicyForObject and ClaimClusterPolicyForObject function
2. Added tests for BuildResourceBinding and BuildClusterResourceBinding function
3. Implemented comprehensive tests for isWaiting, AddWaiting, and RemoveWaiting functions
4. Added tests for OnPropagationPolicyAdd, OnPropagationPolicyUpdate, OnClusterPropagationPolicyAdd and OnClusterPropagationPolicyUpdate functions
5. Added tests for HandlePropagationPolicyDeletion, HandleClusterPropagationPolicyDeletion, HandlePropagationPolicyCreationOrUpdate and HandleClusterPropagationPolicyCreationOrUpdate functions
6. Created mock implementations for various interfaces to facilitate testing

Test Coverage:
pkg/detector/detector.go: 27.83% to 48.1%

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

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.91%. Comparing base (53c00f7) to head (3a0abd2).
Report is 14 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5746      +/-   ##
==========================================
+ Coverage   41.38%   41.91%   +0.52%     
==========================================
  Files         651      653       +2     
  Lines       55259    55484     +225     
==========================================
+ Hits        22867    23254     +387     
+ Misses      30913    30702     -211     
- Partials     1479     1528      +49     

Flag	Coverage Δ
unittests	41.91% <ø> (+0.52%)	⬆️

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[XiShanYongYe-Chang]

/cc @zhzhuang-zju
/assign