Closes#259770Closes#207050
The motivation for the former is to not execute the container as root,
so you don't have to `sudo -i` to perform podman management tasks.
The idea behind healthchecks is to be able to keep the unit in the
activating state until the container is healthy, only then then unit is
marked as active.
The following changes were necessary:
* Move the ctr-id into `/run/${containerName}` to make podman can
actually write to it since it's now in its RuntimeDirectory.
* Make `sdnotify` option configurable (`healthy` for healthchecks that
must pass, default remains `conmon`).
* Set Delegate=yes for `sdnotify=healthy` to make sure a rootless
container can actually talk to sd_notify[1].
* Add a warning that lingering must be enabled to have a `systemd --user`
instance running which is required for the cgroup support to work
properly.
* Added a testcase for rootless containers with both conmon and
healthchecks.
[1] https://github.com/containers/podman/discussions/20573#discussioncomment-7612481
