feat: adding controlPlaneScalingConfig to Cluster

[notSoWiseOldMan]

Reason for this change

controlPlaneScalingConfig was an option added to EKS clusters recently. This was added to CFN and the level 1 structure. This PR adds it to the level 2 construct.

Description of changes

• Added controlPlaneScalingConfig to Cluster.
• Added section to the README
• Added unit tests for basic controlPlaneScalingConfig validation

Describe any new or updated permissions being added

None

Description of how you validated changes

Tested with unit tests. CFN side changes have been tested separately and this change is not doing anything more than just passing through the level 1 cfnCluster properties.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

(This review is outdated)

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

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	Tests	Passed ☑️	Skipped	Failed ❌️
Security Guardian Results	75 ran	73 passed		2 failed

Test	Result
Security Guardian Results
packages/@aws-cdk-testing/framework-integ/test/aws-eks/test/integ.eks-cluster.js.snapshot/aws-cdk-eks-cluster.template.json
iam-no-overly-permissive-passrole.guard	❌ failure
iam-no-world-accessible-trust-policy.guard	❌ failure

• View Security Guardian Results

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

---

	Tests	Passed ✅	Skipped	Failed
Security Guardian Results with resolved templates	75 ran	75 passed

Test	Result
No test annotations available

• View Security Guardian Results with resolved templates

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[aws-cdk-automation]

(This review is outdated)

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[notSoWiseOldMan]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined. Please try merge from main to avoid findings unrelated to the PR.
Tests Passed ✅ Skipped Failed
Security Guardian Results with resolved templates 75 ran 75 passed
Test Result
No test annotations available

* [View Security Guardian Results with resolved templates](https://github.com/aws/aws-cdk/runs/58485001756)

This report shows all passing tests but the one just above it shows some failing. Both are marked as experimental and security guardian is passing locally in my devcontainer. Do we need all experimental security guardian pipelines to pass?