fix(cloudformation-diff): string.replace error on cdk context (#2854)

[michaelmoussa]

Fixes #2854

@aws-sdk/cloudformation-diff depended on version ^2.1.1 of the string-width library in v0.28.0 of aws-sdk. In v0.29.0, the dependency was bumped to ^4.1.0, which inadvertently broke the cdk context command as reported in: #2854.

The current version of string-width executes a string replacement, which ends up failing when a non-string (such as the int row numbers of the cdk context values). This did not previously occur, as the typecheck for string would cause the function to return early and report zero-length.

The easiest solution here is to cast these values to string, which has the beneficial side effect of ensuring that their character lengths are taken into consideration rather than being defaulted to 0 as they had previously been.

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re: PR checklist, I would need some assistance with the Testing, as I don't have a fully provisioned local development environment for CDK available. Title and Description is all set, though, and Docs / Sensitive Modules are not applicable here.

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Pull Request Checklist

• Testing
  • Unit test added (prefer not to modify an existing test, otherwise, it's probably a breaking change)
  • CLI change?: coordinate update of integration tests with team
  • cdk-init template change?: coordinated update of integration tests with team
• Docs
  • jsdocs: All public APIs documented
  • README: README and/or documentation topic updated
  • Design: For significant features, design document added to design folder
• Title and Description
  • Change type: title prefixed with fix, feat and module name in parens, which will appear in changelog
  • Title: use lower-case and doesn't end with a period
  • Breaking?: last paragraph: "BREAKING CHANGE: <describe what changed + link for details>"
  • Issues: Indicate issues fixed via: "Fixes #xxx" or "Closes #xxx"
• Sensitive Modules (requires 2 PR approvers)
  • IAM Policy Document (in @aws-cdk/aws-iam)
  • EC2 Security Groups and ACLs (in @aws-cdk/aws-ec2)
  • Grant APIs (only if not based on official documentation with a reference)

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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.

[RomainMuller]

Nice catch! Thank you for this contribution!