feat: allow setting service annotations via helm chart

[jamesduffy]

Fixes #N/A

Description
Allows setting annotations on the karpenter service. We need this so that we can add annotations to setup datadog to monitor karpenter. There are probably other use cases.

How was this change tested?

Generated a helm chart locally with the additional values:

service:
  annotations:
    ad.datadoghq.com/service.checks: |
      {
        "karpenter": {
          "cluster_check": true,
          "init_config": {},
          "instances": [
            {
              "openmetrics_endpoint": "http://%%host%%:8000/metrics",
              "exclude_metrics": [
                "^karpenter\\.go\\..*$"
              ]
            }
          ]
        }
      }

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

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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[jmdeal]

What's preventing you from using the existing additionalAnnotations field? Unless absolutely necessary, we'd like to avoid additional configuration in the helm chart.

[jamesduffy]

What's preventing you from using the existing additionalAnnotations field? Unless absolutely necessary, we'd like to avoid additional configuration in the helm chart.

additionalAnnotations adds the annotations to a lot of different things. This would be picked up from the Datadog agent as separate checks and instead of running just one check for Karpenter it would run duplicate checks for each place additionalAnnotations is injected. Therefore, we would need a way to add the annotation in a single place. Datadog annotations are often on the service.

[github-actions]

This PR has been inactive for 14 days. StaleBot will close this stale PR after 14 more days of inactivity.

[jamesduffy]

@jmdeal I would like to move forward with this if my explanation makes sense.