board/MynaPlayer odyssey: add basic service to mark boot as good with rauc. #24

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.

board/MynaPlayer odyssey: add basic service to mark boot as good with rauc.