Improve test coverage of pkg/descheduler

[anujagrawal699]

Description:
This PR enhances the test coverage for the pkg/descheduler package by adding a new test file pkg/descheduler/core/helper_test.go and improving test coverage of all test files in pkg/descheduler.

Changes:

1. Added new test file for pkg/descheduler/core/helper.go.
2. Added meaningful test cases for functions which were not covered before by the tests and improved test coverage of pkg/descheduler/core/ from 13.75% to 85.5%.
3. Added meaningful test cases for functions which were not covered before by the file descheduler_test.go, significantly improving its test coverage.

What type of PR is this?
/kind failing-test
/kind feature

What this PR does / why we need it:
Enhances the functionality of the pkg/descheduler package by improving the robustness of event handling and connection management.

Which issue(s) this PR fixes:
Fixes a part of #5235

Does this PR introduce a user-facing change?:

NONE

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.28%. Comparing base (6e9136d) to head (810ca89).
Report is 30 commits behind head on master.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5364      +/-   ##
==========================================
+ Coverage   28.49%   29.28%   +0.78%     
==========================================
  Files         632      632              
  Lines       43856    43862       +6     
==========================================
+ Hits        12497    12844     +347     
+ Misses      30455    30089     -366     
- Partials      904      929      +25     

Flag	Coverage Δ
unittests	29.28% <ø> (+0.78%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[XiShanYongYe-Chang]

/assign

[anujagrawal699]

@XiShanYongYe-Chang CI Workflow?

[XiShanYongYe-Chang]

/retest

[XiShanYongYe-Chang]

Thanks @anujagrawal699
Good job!
/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• pkg/descheduler/OWNERS [XiShanYongYe-Chang]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[XiShanYongYe-Chang]

Sorry, my bad, I forgot to ask you to help squash the commits into one before merging the code.

[anujagrawal699]

Sorry, my bad, I forgot to ask you to help squash the commits into one before merging the code.

I won't be able to squash it after merging? Also, i forgot to mention this PR increased test coverage of project by 0.79%.

[XiShanYongYe-Chang]

Yes, it can't be compressed anymore after the merge.

[anujagrawal699]

Yes, it can't be compressed anymore after the merge.

I'll keep that in mind from next PR's.