tree-wide: replace uses of splitString "." with lib.versions

Quoting from the splitString docstring:

   NOTE: this function is not performant and should never be used.

This replaces trivial uses of splitString for splitting version
strings with the (potentially builtin) splitVersion.

pkgs/development/lua-modules/overrides.nix

@@ -29,7 +29,7 @@ with super;
     # Parse out a version number without the Lua version inserted
     version = with pkgs.lib; let
       version' = super.cqueues.version;
-      rel = splitString "." version';
+      rel = splitVersion version';
       date = head rel;
       rev = last (splitString "-" (last rel));
     in "${date}-${rev}";