fix(cloudfront): metrics not including correct region config

[georeeve]

Issue # (if applicable)

Closes #19245.

Reason for this change

CDK currently does not include the required Region: 'Global' dimension in the dimensions object for its CloudFront metric() functions. This means the metrics do not work without having to overwrite the dimensions object manually (losing the benefit of the distribution ID being automatically populated).

I have also set the region prop to default to us-east-1, as this is also required. It saves the client from having to specify it manually, although at least that doesn't involve overwriting the object.

https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/programming-cloudwatch-metrics.html#cloudfront-metrics-global-values

Description of changes

Add Region: 'Global' dimension, and region: 'us-east-1' by default to code and tests.

Describe any new or updated permissions being added

Description of how you validated changes

Manual testing and running the test suite

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]

The pull request linter fails with the following errors:

❌ Fixes must contain a change to an integration test file and the resulting snapshot.

If you believe this pull request should receive an exemption, please comment and provide a justification. A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed, add Clarification Request to a comment.

✅ A exemption request has been requested. Please wait for a maintainer's review.

[georeeve]

Exemption Request - The existing integration tests cover the metrics just fine (and I have updated the snapshots to match the new defaults), just the metrics weren't working on CloudWatch due to the missing region props.