runner: Expose dind runner dockerd logs via stdout/stderr (#2082)

* runner: Expose dind runner dockerd logs via stdout/stderr

We've been letting supervisord to run dockerd within the dind runner container presuming it would avoid producing zombie processes. However we used dumb-init to wrap supervisord to wrap dockerd. In this picture supervisord might be unnecessary and dumb-init is actually a correct pid 0 for containers.

Rmoving supervisord removes this unnecessary complexity, while saving a little memory, and more importantly logs from dockerd is exposed via stdout/stderr of the container for easy access from kubectl-logs, fluentd, and so on.

runner/actions-runner-dind-rootless.ubuntu-22.04.dockerfile

@@ -27,7 +27,6 @@ RUN apt-get update -y \
     iproute2 \
     iptables \
     jq \
-    supervisor \
     sudo \
     uidmap \
     unzip \