✨ output Toplevel runtime exception as Errors instead of standard output values

[AlexisHamon]

In Ocaml top-level standard versions, runtime exceptions are treated as standard values.
However, we can treat those values as exceptions for the user in order to see them with error formatting.

In this case, I colorize the runtime exceptions as errors, but we can easily switch behavior.

Example of code impacted :

exception Test;;

raise Test;;