Add Error-like effect without Catch

[googleson78]

Let's generalise Fail to be

newtype Fail e m a = Fail e

instead.

My motivation is that I need to have custom types for failures, but I'm never going to be Catching, so I don't want to bother with handling that in my code, and so Error is not very useful.

[KingoftheHomeless]

Fail's not the right fit for that. Fail's purpose is to provide the MonadFail instance of Sem; nothing else.
However, I could consider the addition of a new effect:

newtype Abort e m a where
  Abort :: e -> Abort e m a

(modulo naming)