fix: host network configuration on linux (#3394)

Docker on Linux doesn't understand `host.docker.internal` automatically.
We need to add it as an extra host using `extra_hosts`. This was caught
by @mrasu in his issue #3393.

examples/tracetest-agent/pokeshop/docker-compose.yaml

@@ -108,3 +108,5 @@ services:
       - "/otel-local-config.yaml"
     volumes:
       - ./collector.config.yaml:/otel-local-config.yaml
+    extra_hosts:
+      - "host.docker.internal:host-gateway"