Add `--no-daemon` or `--foreground` option for supervised systems

I've recently moved most of my servers and VMs to Artix Linux (a derivative of Arch Linux, sans systemd). I chose the `runit` system for my init and process supervision system on my Artix boxes (s6 is a mess, and OpenRC, well, it's not a supervision system). This has been working great up until I attempted to move my web server from Gentoo to Artix. Everything went smoothly, except for `cloudflared`.

I use `cloudflared` for connecting to the Cloudflare network, which caches, and serves my websites. It's a traditional use of Argo tunnel, namely, my web server is *not* accessible from the Internet, only from CF via Argo tunnel.

Basically, If CF were to add a `--no-daemon` option, this would allow me to launch the process in a supervised manner, meaning that there is a parent process which receives SIGCHLD and can automatically restart the dead process. Additionally, this means I could allow `cloudflared` to automagically update itself, and once complete, it can just exit. No races, no PID tracking, and more importantly, no dropped log messages. (runit handles that).