base: Add `Control.Exception.throwIOLeft` utility

The main motivation for this utility is to simplify working with actions of type IO (Either e a)

An alternative approach could have been to directly implement a utility of type:

??? :: IO (Either e a) -> IO a

… but I went with the current type for two reasons:

• I conducted a poll to see which version people preferred:

  https://twitter.com/GabriellaG439/status/1428589302951268355

• The current version also has nicer theoretical properties, like being a monad morphism

  There's another property I didn't mention in the documentation, which is that throwLeft distributes over exception handling, too:

  throwIOLeft (m `catchError` \x -> f x) =
    throwIOLeft m `catchError` \x -> throwIOLeft (f x)
  
  throwIOLeft (throwError e) = throwError e

• It's fairly ergonomic to implement the latter type in terms of the current type

  The latter type is just (>>= throwIOLeft)