add more e2e for WorkloadRebalancer

[chaosi-zju]

What type of PR is this?

/kind failing-test

What this PR does / why we need it:

add more e2e for WorkloadRebalancer

Which issue(s) this PR fixes:

Fixes part of #4840

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.32%. Comparing base (fcb46bb) to head (a850b14).
Report is 2 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4961      +/-   ##
==========================================
+ Coverage   53.31%   53.32%   +0.01%     
==========================================
  Files         252      252              
  Lines       20485    20489       +4     
==========================================
+ Hits        10921    10926       +5     
  Misses       8842     8842              
+ Partials      722      721       -1     

Flag	Coverage Δ
unittests	53.32% <ø> (+0.01%)	⬆️

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[chaosi-zju]

CC @XiShanYongYe-Chang

[XiShanYongYe-Chang]

/assign

[XiShanYongYe-Chang]

It's generally LGTM.

[XiShanYongYe-Chang]

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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