Enable type-level distinctions between operations that thread state and those that don’t.

We removed the Resource effect in #268 because of its unlawful interactions with the State effect. This was the right move, but it is also a bummer, because the Resource effect is extremely useful.

What would be ideal is a system like polysemy’s Tactics module, which used in concert with Resource and the withLowerToIO system provided by their forklift implementation. Failing that, it would be ideal to have some type-level mechanism that rejects calls to functions like get and put inside a finally block:

finally :: (Has Resource sig, Carrier sig m, IsStatelessIn n m) 
  => m a
  -> n a
  -> m a

where this hypothetical IsStatelessIn construct is fulfilled by Reader but not by State. Or something. Either approach would be acceptable to me; that would enable us to deprecate fused-effects-exceptions and welcome Resource back into the fold.