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/Entities/Marker.hs

@@ -11,7 +11,6 @@ import           Brick.Widgets.Core (raw)
 --------------------------------------------------------------------------------
 import           Xanthous.Game.State
 import           Xanthous.Data.Entities (EntityAttributes(..))
-import           Xanthous.Data.EntityChar (style)
 --------------------------------------------------------------------------------
 
 -- | Mark on the map - for use in debugging / development only.