Implement OTEL Metrics emissions.

[davinchia]

Tell us about the problem you're trying to solve

Follow up to #12906 .

Implement OTEL Metric emission. OTEL is a generic metrics framework with multiple plugins for maximum compatibility with the various metrics frameworks.

The approach here is to only implement general OTEL metric emissions. We do not include the OTEL collector or specific exporters with the Airbyte deployment. This is left up to users.

This should be reviewed by one OSS team member.

Describe the solution you’d like

• Implement metric emission to the general OTEL collector. See spike here.
• Add an env var to switch on which underlying implementation is used. We default to OTEL emission unless a specific environment variable is passed in for Datadog. This env var will be used by Cloud.
• Add documentation on how to set up the OTEL collector for the docker deployment and the Kubernetes deployment, as well as how to set up the individual exporters. Using Prometheus as an E2E example for Kube is probably sufficient.
• Make sure that we have robust testing in place, since in Cloud we won't have this turned on and issues can go unnoticed