fix(metrics): AWS CloudWatch Embedded Metrics Dimensions

[jshlbrd]

Description

• Fixes dimensions in the AWS CloudWatch Embedded Metrics destination

Motivation and Context

This fixes a bug that causes multiple attributes to be incorrectly assigned to dimensions in the metric (discovered while testing #178 in a production pipeline). The fix has these dimensions:

"Dimensions":[["FunctionName","FreshnessType"]]

The incorrect dimensions are:

"Dimensions":[["FunctionName"],["FreshnessType"]]

This bug doesn't impact the metric value, but it does affect filters in CloudWatch (and may affect downstream systems).

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.