[Feature] Add support for rootless docker

[89luca89]

Right now we have support for rootless podman, but docker only works in rootful mode.
This can create unpleasant situations like described in #201

Right now rootless docker is not working like podman and using it prevents a lot of integration with the system, like use of --network host

This issue will keep track of the development of rootless docker and the possibility to integrate it

[catuhana]

What's the status of this?

[trofosila]

@89luca89 any progress on this?

[frafra]

I am able to use distrobox with rootless mode, but there is an error setting up the user:

OCI runtime exec failed: exec failed: unable to start container process: unable to setup user: invalid argument: unknown

Nonetheless, since the container root user is mapped as a regular user, this is not a problem, and I can enter into the container using docker exec "$container" /bin/bash.