Introduce the WithResource node

(Resources aren't handled yet.)
Get rid of TestMap
Get rid of ResourceName
Actually handle resources
Drop Typeable constraint from ResourceSpec for now
withResource
Fix core-tests (add an arg to foldTestTree)
Test resources
More robust resource release

Make sure that resources are released before the status var is updated, because
that could lead e.g. to the main thread exiting
Update core-tests.cabal
tasty 0.5