Add a function to try things until first 'Result'

[chshersh]

The proposed type:

trials :: Monad m => [m a] -> (a -> m (Trial e b)) -> m (Trial e b)

What should be the name? trials tryUntil firstResult ...

[chshersh]

In the real use case, I have two functions:

foo :: IO (Trial e Config)
bar :: IO (Trial e Config)

I desperately want to write in a nice syntax something like this:

foo <|> bar

But Alternative instance for IO doesn't work that way... We can introduce a new operator, like, lazy monadic alternative with the following type and semantics:

<||> :: Monad m => m (Trial e a) -> m (Trial e a) -> m (Trial e a)

• If the first Trial is Result then don't perform second action, otherwise perform second and use <|> (or <>, depending on Change Alternative instance #50) on both values.