fix(custom-resource-handlers): better fallback for require failures

[glitchassassin]

Issue # (if applicable)

Closes #30067.

Reason for this change

Fallback to existing AWS SDK import misses a rare/flaky edge case where the npm install passes, but the subsequent require fails

Description of changes

Fall back to the pre-existing AWS SDK if requiring the latest version fails

Description of how you validated changes

• Fixed no-op test "installs the latest SDK"
• Added test "falls back to installed sdk if require fails"

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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[sumupitchayan]

@glitchassassin thanks for the PR, can you check out the build failure? Looks like you may have forgotten to run the integ tests and update the snapshots

[glitchassassin]

Thanks @sumupitchayan, @GavinZZ is helping me out with the integration tests

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

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 2dd9cd3
• Result: SUCCEEDED
• Build Logs (available for 30 days)

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