Nix-based CI

This leans on @mpickering's ghc-artefact-nix and head.hackage to provide testing of Hackage packages using GHC binary distributions.

patches/aeson-1.4.2.0.cabal

@@ -107,9 +107,9 @@ library
     containers       >= 0.4.2.1 && < 0.7,
     deepseq          >= 1.3.0.0 && < 1.5,
     ghc-prim         >= 0.2     && < 0.6,
-    template-haskell >= 2.7.0.0 && < 2.15,
+    template-haskell >= 2.7.0.0 && < 2.16,
     text             >= 1.2.3.0 && < 1.3,
-    time             >= 1.4     && < 1.9
+    time             >= 1.4     && < 1.10
 
   -- Compat
   build-depends: