WIP: Add Traefik metrics

What does this MR do?

This adds support for traefik request metrics.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Current additional_metrics support NGINX, HAProxy and ELB. Traefik is a popular choice for Kubernetes apps and is available as an Ingress controller.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Edited by username-removed-10941

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