fix(xan): fix compat with new base+ghc

A couple of changes necessary to get things working with both ghc 8.8.3
and the new base:

- Explicitly import fail from Control.Monad.Fail in the prelude, since
  it's there instead of the base prelude now
- GHC no longer allows type family equality constraints in quantified
  constraints - which is a bummer - but is avoidable in the one case
  where it was happening
- Explicitly import a constructor from Data.List.NonEmpty

Change-Id: Ia06fc724ddc2d6a3f9024c047ed55eea40bcf408
Reviewed-on: https://cl.tvl.fyi/c/depot/+/744
Tested-by: BuildkiteCI
Reviewed-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/glittershark/xanthous/src/Xanthous/Data.hs

@@ -100,7 +100,7 @@ import           Xanthous.Prelude hiding (Left, Down, Right, (.=), elements)
 import           Linear.V2 hiding (_x, _y)
 import qualified Linear.V2 as L
 import           Linear.V4 hiding (_x, _y)
-import           Test.QuickCheck (Arbitrary, CoArbitrary, Function, elements)
+import           Test.QuickCheck (CoArbitrary, Function, elements)
 import           Test.QuickCheck.Arbitrary.Generic
 import           Data.Group
 import           Brick (Location(Location), Edges(..))