As developer i want to create a function's route from func.yml (explicitly)

[denismakogon]

A long time ago we did that but implicitly and we wiped that functionality out.
So, adding --from-file to fn routes create would bring better UX unless you do fn deploy all the time.
At this time let's do that explicitly. If --from-file is there, use func.yml, if that is not - use the rest of args, if both mentioned - conflit, abort.