feat: cloudwatch metrics tags

[heilhead]

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Description

This adds the Tag dimension to all metrics exported by the sign client canary. It's a requirement for the relay to be able to run multiple canaries with different configurations and be able to distinguish resulting metrics.

Type of change

• Chore (non-breaking change that addresses non-functional tasks, maintenance, or code quality improvements)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Draft PR (breaking/non-breaking change which needs more work for having a proper functionality [Mark this PR as ready to review only when completely ready])
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How has this been tested?

Untested.

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Checklist

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[arein]

This will most likely break Relay metrics so give on-call a heads-up
Relay metrics will then needs to set the default dimension