Rollup merge of #92360 - jackh726:param-heuristics-1, r=davidtwco

Some cleanups around check_argument_types

Split out in ways from my rebase/continuation of #71827

Commits are mostly self-explanatory and these changes should be fairly straightforward

src/test/ui/c-variadic/variadic-unreachable-arg-error.rs

@@ -0,0 +1,14 @@
+// check-pass
+
+#![feature(c_variadic)]
+
+extern "C" {
+    fn foo(f: isize, x: u8, ...);
+}
+
+fn main() {
+    unsafe {
+        // FIXME: Ideally we could give an unreachable warning
+        foo(1, loop {}, 1usize);
+    }
+}