fix(cloudformation-diff): cdk diff throws toUpperCase is not a function when ipProtocol is a number

[gastonsilva]

Fix the describe protocol method when running a diff with a processed existing cloudformation template that has a security group rule with ipprotocol = -1

Closes #28021

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[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

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[gastonsilva]

Exemption Request
Cannot find a way to implement an integration test for this scenario

[vinayak-kukreja]

Hey @gastonsilva , thank you for your contribution.

I am confirming with the team if an exemption could be granted for this PR. Other than that, the changes looks good to me.

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

[aws-cdk-automation]

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• Commit ID: 091bb1d
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