Swap arguments in actor's loop function.

[hayleigh-dot-dev]

In Gleam the convention is for the "subject" or data being manipulated to be the first argument of a function. For actors, this convention is violated and we have the message as the first argument.

Getting this right for the sake of consistency / knowledge transfer would be a win!

[lpil]

I think this would be a good thing to sneak in with the upcoming API changes