nix: 2.18 -> 2.22

I tested this version on my system without any noticable issues, but on
the other hand it has better error handling i.e. for infinite recursion.

This version has been now also cooking in the nix-install-action for 2
weeks: cachix/install-nix-action#206

pkgs/tools/package-management/nix/default.nix

@@ -207,7 +207,7 @@ in lib.makeExtensible (self: ({
     else
       nix;
 
-  stable = addFallbackPathsCheck self.nix_2_18;
+  stable = addFallbackPathsCheck self.nix_2_22;
 } // lib.optionalAttrs config.allowAliases (
   lib.listToAttrs (map (
     minor: