fix(autoscaling): cooldown cannot be set with step scaling actions

[GavinZZ]

Issue # (if applicable)

Closes #29779

Reason for this change

cooldown cannot be set on step scaling and can cause deployment failure in certain regions.

Description of changes

Deprecate the property and ignore the value. Give a warning.

Description of how you validated changes

Unit test added.

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

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: a3e86ba
• Result: SUCCEEDED
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