Backport of Datadog Integration Acceptance Tests / Bug fixes into release/1.4.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #3685 to be assessed for backporting due to the inclusion of the label backport/1.4.x.

The below text is copied from the body of the original PR.

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Changes proposed in this PR

• Introduce datadog integration acceptance testing with Datadog API
  • Consul Integration
  • DogstatsD (Unix Domain Sockets)
  • DogstatsD (UDP)
  • Openmetrics Prometheus
  • OTLP Collection Integration (HTTP)
  • OTLP Collection Integration (gRPC)
• Fix some bugs surrounding the Openmetrics and Consul Integration Checks
  • Consul Checks also require prometheus.io annotations to be removed while enabled to avoid conflicts w/ dd-agent
  • Fix Openmetrics and Consul Integration check URLs to use consul.fullname-server helper template for accurate consul API access
  • Fix OTLP collection for telemetry-collector-deployment.yaml to include OTEL_EXPORTER_OTLP_ENDPOINT env variable for proper Datadog tag ingestion

How I've tested this PR

• Ran: make bats-test for templating updates
• Ran acceptance tests for new Datadog framework and test scenarios following CONTRIBUTING.md guide.

How I expect reviewers to test this PR

• Review acceptance tests and see if they're worth even having in the repository. They add a few more go dependencies for Datadog client API access
  • The tests access the datadog agent's local API with datadog dogstatsd stats enabled to parse metrics output from the collection event.
  • This testing leverages the Datadog fake-intake image to simulate traffic ingestion and remove the requirement to have to use an API and APP key.

Checklist

• Tests added
• CHANGELOG entry added

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Overview of commits

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