This adds a service that marks the system as good when booting up that has the following:

- Starts after sshd, login prompt on serial console, and NetworkManager have all started up.
- Requires those three services to be up, not simply wanting them.
- If any of them fail to start, the rauc-mark-good.service fails with the result dependency and the rauc-failure.service included by this commit is triggered, and immediately reboots the system.