[backplane] support OTEL spec for env vars

[theRealWardo]

see the OpenTelemetry specification

backplane can be configured with environment variables to support relaying to another OTLP ingestion endpoint. for example, if a Datadog agent or Vector instance is running on the host then a Kubernetes deployment of backplane can be provided the extraEnv vars of something like:

 - name: HOST_IP
   valueFrom:
     fieldRef:
       fieldPath: status.hostIP
 - name: OTEL_EXPORTER_OTLP_ENDPOINT
   value: "$(HOST_IP):4317"
- name: OTEL_EXPORTER_OTLP_PROTOCOL
   value: "gprc"
- name: OTEL_EXPORTER_OTLP_INSECURE
   value: "true"