feat: [telegraf] allow multiple Prometheus outputs in the service

[aliasboink]

I have a need for multiple Prometheus outputs on the Telegraf helm-chart.

  outputs:
    - prometheus_client:
        listen: ":30000"
        metric_version: 2
        path: "/metrics"
    - prometheus_client:
        listen: ":9273"
        metric_version: 2
        path: "/metrics"
    - prometheus_client:
        listen: ":9274"
        metric_version: 1
        path: "/metrics"

This configuration causes an error only in the Kubernetes service, as shown here: #693

The implemented has been tested and works as expected:

Please notify me if there's anything else I need to for this PR.

[aliasboink]

Since the initial creation of this PR the change has been tested in production and it works as intended.