feat(xan): Use haskell-language-server

Use haskell-language-server instead of haskell-ide-engine for Xanthous.

Change-Id: I7ef1433d5cd561e659fc06b3f373a6f29dfa5690
Reviewed-on: https://cl.tvl.fyi/c/depot/+/904
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>
Reviewed-by: BuildkiteCI

users/glittershark/xanthous/hie.yaml

@@ -0,0 +1,10 @@
+cradle:
+  cabal:
+    - path: './src'
+      component: 'lib:xanthous'
+    - path: './test'
+      component: 'test:test'
+    - path: './src'
+      component: 'exe:xanthous'
+    - path: './bench'
+      component: 'bench:benchmark'