Added unit tests for scheduler's cache package

[anujagrawal699]

Description:
This PR adds comprehensive unit tests for the scheduler's cache package, focusing on testing the core functionality of cache operations. These tests improve code coverage and ensure reliable behavior of a critical component that manages node/pod state and snapshot management for scheduling decisions.

Additions:

1. pkg/util/lifted/scheduler/cache/cache_test.go

Test coverage:

1. pkg/util/lifted/scheduler/cache/cache_test.go : 0% to 77.4%

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

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.85%. Comparing base (b3d3bcd) to head (085b433).
Report is 4 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5792      +/-   ##
==========================================
+ Coverage   42.36%   42.85%   +0.48%     
==========================================
  Files         656      656              
  Lines       55884    55884              
==========================================
+ Hits        23676    23947     +271     
+ Misses      30689    30390     -299     
- Partials     1519     1547      +28     

Flag	Coverage Δ
unittests	42.85% <ø> (+0.48%)	⬆️

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[XiShanYongYe-Chang]

Thanks~
/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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