Automated cherry pick of #5976: Only genrate ETCD PKI for local ETCD setup

[jabellard]

Cherry pick of #5976 on release-1.12.
#5976: Only genrate ETCD PKI for local ETCD setup
For details on the cherry pick process, see the cherry pick requests page.

`karmada-operator`: Fixed the issue that external ETCD certificate be overwritten by generated in-cluster ETCD certificate.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 19.35484% with 25 lines in your changes missing coverage. Please review.

Project coverage is 46.50%. Comparing base (3e154f7) to head (2032eb7).

Files with missing lines	Patch %	Lines
operator/pkg/tasks/init/upload.go	0.00%	19 Missing ⚠️
operator/pkg/certs/certs.go	0.00%	6 Missing ⚠️

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Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.12    #6008      +/-   ##
================================================
- Coverage         46.51%   46.50%   -0.02%     
================================================
  Files               664      664              
  Lines             54785    54789       +4     
================================================
- Hits              25485    25481       -4     
- Misses            27673    27680       +7     
- Partials           1627     1628       +1     

Flag	Coverage Δ
unittests	46.50% <19.35%> (-0.02%)	⬇️

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[RainbowMango]

/lgtm
/approve

[karmada-bot]

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