refactor(tvix/eval): rename UnexpectedArgument{,Formals}

There's other places where unexpected arguments can be provided, like
in builtins.

Make space for that error type.

Change-Id: Ic831497a3a1dd36a3a184bedadcf1374bf0ae6db
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11876
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/eval/src/vm/mod.rs

@@ -797,7 +797,7 @@ where
                         if !formals.contains(arg) {
                             return frame.error(
                                 self,
-                                ErrorKind::UnexpectedArgument {
+                                ErrorKind::UnexpectedArgumentFormals {
                                     arg: arg.clone(),
                                     formals_span: formals.span,
                                 },