ci: apply the standalone broker configuration from env

[mdeltito]

bin/pulsar standalone does not read the PULSAR_PREFIX_* variables, so none of the broker settings the workflow passes were actually applied. This worked because all of the env vars match the defaults.

Also removes the advertisedListeners env var, which was invalid its prior form and the override is not needed anyway.

❯ docker run --name probe -d -e PULSAR_PREFIX_advertisedAddress=9.9.9.9 \ # <---
          apachepulsar/pulsar:3.0.8 bin/pulsar standalone
  sleep 20
  docker exec probe curl -s http://127.0.0.1:8080/admin/v2/brokers/configuration/runtime \
          | tr ',' '\n' | grep '"advertisedAddress"'
  docker rm -f probe

"advertisedAddress":"localhost" # <---

❯ docker run --name probe -d -e PULSAR_PREFIX_advertisedAddress=9.9.9.9 \ # <---
          apachepulsar/pulsar:3.0.8 bash -c "bin/apply-config-from-env.py conf/standalone.conf && bin/pulsar standalone"
  sleep 20
  docker exec probe curl -s http://127.0.0.1:8080/admin/v2/brokers/configuration/runtime \
          | tr ',' '\n' | grep '"advertisedAddress"'
  docker rm -f probe

"advertisedAddress":"9.9.9.9" # <---

[mdeltito]

closing in favor of #428 which folds in this change