adapting webhook service name in the logger
adapting webhook service name in the logger

Instead of hardcoding "webhook-pipeline", reading it from the env if
specified to be consistent.

The webhook logs will now have the consistent service name in the logs,
i.e. "logger":"tekton-pipelines-webhook.*" or the name specified in
WEBHOOK_SERVICE_NAME env. variable instead of "logger":"webhook-pipeline.*"

tektoncd/pipeline,tektoncd/pipeline