operator: Customizable Certificate Configuration

[zhzhuang-zju]

What type of PR is this?
/kind feature
/kind api-change

What this PR does / why we need it:
This PR introduces CertConfig to the Karmada API, thereby providing karmada-operator with the capability to customize the certificate's validity period and PublicKeyAlgorithm.
For example, if the relevant configuration for CR karmada is as follows:

customCertificate:
  certConfig:
    expiry: 365
    notAfter: 2026-01-01T00:00:00Z
    publicKeyAlgorithm: ECDSA

Then the generated certificate is as follows:

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 1174342019010031212 (0x104c19d827e86e6c)
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN = karmada
        Validity
            Not Before: Jan 1 00:00:00 2024 GMT
            Not After : Jan  1 00:00:00 2025 GMT
        Subject: O = system:masters, CN = system:admin
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

`karmada-operator`: introduces `CertConfig` to the `Karmada` API, thereby providing `karmada-operator` with the capability to customize the certificate's validity period and PublicKeyAlgorithm.

[karmada-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign poor12, rainbowmango for approval. For more information see the Kubernetes Code Review Process.

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

Needs approval from an approver in each of these files:

• charts/OWNERS
• operator/OWNERS
• operator/pkg/apis/OWNERS

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[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 49.15254% with 30 lines in your changes missing coverage. Please review.

Project coverage is 48.16%. Comparing base (8457cd2) to head (03aad2b).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
operator/pkg/tasks/init/cert.go	17.64%	13 Missing and 1 partial ⚠️
operator/pkg/init.go	0.00%	9 Missing ⚠️
operator/pkg/apis/operator/v1alpha1/defaults.go	81.25%	2 Missing and 1 partial ⚠️
operator/pkg/certs/certs.go	81.25%	2 Missing and 1 partial ⚠️
operator/pkg/tasks/init/upload.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5944      +/-   ##
==========================================
+ Coverage   48.10%   48.16%   +0.05%     
==========================================
  Files         663      664       +1     
  Lines       54769    54851      +82     
==========================================
+ Hits        26349    26421      +72     
- Misses      26711    26712       +1     
- Partials     1709     1718       +9     

Flag	Coverage Δ
unittests	48.16% <49.15%> (+0.05%)	⬆️

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