Added new tests and refractored old in pkg/descheduler/core

[anujagrawal699]

Description:
This PR introduces new test cases and refractors the old tests for the core components of descheduler. It adds new test cases in pkg/descheduler/core/filter_test.go and refactors old tests in pkg/descheduler/core/helper_test.go to a table-driven approach, thus testing more scenarios. The new tests aim to improve code reliability, maintainability, and overall test coverage for core descheduling operations.

Modifications:

1. pkg/descheduler/core/filter_test.go:

• Added new test cases for testing filter bindings.
• Added new test cases for validating GVK (Group Version Kind) and placement annotations.
• Introduced tests for handling invalid JSON in placement annotations and various edge cases.

2. pkg/descheduler/core/helper_test.go:

• Refactored TestNewSchedulingResultHelper to use table-driven tests, covering more scenarios including invalid status handling.
• Updated TestSchedulingResultHelper_FillUnschedulableReplicas to use table-driven tests and mock estimators for better coverage.
• Refactored TestSchedulingResultHelper_GetUndesiredClusters to use table-driven tests.
• Updated TestGetReadyReplicas to cover more scenarios, including missing fields and invalid JSON.
• Introduced a mock implementation of UnschedulableReplicaEstimator for testing purposes.

Test Coverage:

1. pkg/descheduler/core/filter_test.go : 85% to 100%
2. pkg/descheduler/core/helper_test.go : 76.17% to 98.10%

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 35.24%. Comparing base (62ae95e) to head (fc8b905).
Report is 6 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5649      +/-   ##
==========================================
+ Coverage   35.21%   35.24%   +0.03%     
==========================================
  Files         645      645              
  Lines       44885    44885              
==========================================
+ Hits        15806    15820      +14     
+ Misses      27847    27839       -8     
+ Partials     1232     1226       -6     

Flag	Coverage Δ
unittests	35.24% <ø> (+0.03%)	⬆️

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[XiShanYongYe-Chang]

/assign

[XiShanYongYe-Chang]

Good Job!
/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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