Added tests for validateclustertaints.go and validatingmcs.go

[anujagrawal699]

Description:
This PR introduces unit tests for the cluster taints validation and MCS (Multi-Cluster Services) validation functions in the pkg/util/lifted package. These additions aim to increase code reliability, maintainability, and test coverage for the cluster taints and MCS validation logic.

Additions:

1. pkg/util/lifted/validateclustertaints_test.go
2. pkg/util/lifted/validatingmcs_test.go

Test Coverage:

1. pkg/util/lifted/validateclustertaints.go: 0.00% to 100%
2. pkg/util/lifted/validatingmcs.go: 0.00% to 100%

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 37.84%. Comparing base (201409c) to head (b30b04f).
Report is 8 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5684      +/-   ##
==========================================
+ Coverage   37.75%   37.84%   +0.08%     
==========================================
  Files         649      649              
  Lines       45133    45133              
==========================================
+ Hits        17042    17081      +39     
+ Misses      26795    26755      -40     
- Partials     1296     1297       +1     

Flag	Coverage Δ
unittests	37.84% <ø> (+0.08%)	⬆️

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[XiShanYongYe-Chang]

/assign

[XiShanYongYe-Chang]

How about add a blank line before this test func.

[XiShanYongYe-Chang]

/lgtm
/approve

[karmada-bot]

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

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