prometheus.exporter.cadvisor: Add Podman Support

[dmennecke1]

Request

Currently, there appears to be no official support for Podman within the prometheus.exporter.cadvisor component. While a docker_host flag is available, there is no equivalent podman_host option. However, it is possible to retrieve Podman container metrics directly using cAdvisor.

podman run \
  --name=cadvisor \
  -v /:/rootfs:ro \
  -v /etc/machine-id:/etc/machine-id:ro \
  -v /var/run:/var/run:ro \
  -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
  -v /dev/disk/:/dev/disk:ro \
  -v /var/lib/containers:/var/lib/containers:ro \
  -v /var/lib/dbus/machine-id:/var/lib/dbus/machine-id:ro \
  --privileged=true \
  --device=/dev/kmsg \
  -d \
  gcr.io/cadvisor/cadvisor:v0.50.0 \
  --podman=unix:///var/run/user/1001/podman/podman.sock \
  -docker_only \
  --store_container_labels=true

Use case

Currently, I need both cAdvisor (metrics) and Alloy (to process and push my file-based container logs). However, since Alloy includes a cAdvisor component, I would prefer to use Alloy alone.