Support per-ingress opentelemetry service naming

[davidegreenwald]

Previously, the deprecated open_tracing supported custom per-ingress naming for services in this format:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: foo-service
  annotations:
    nginx.ingress.kubernetes.io/configuration-snippet: |
      opentracing_tag "service.name" "foo-service";

This functionality is now missing with opentelemetry.

Additionally, adding this as a configuration snippet can be problematic because, as we saw removing open_tracing from our ingress controllers, the orphaned setting will then throw errors if it isn't caught and removed everywhere first.

To have opentelemetry support reach feature parity and avoid this footgun behavior, I'm requesting support for the annotation:

nginx.ingress.kubernetes.io/otel-service-name

to be used on a per-ingress basis. If a configuration snippet is the only way, that would be helpful.

Thanks!