bindgen! takes anonymous map parameters by value with borrowed contents #14831

For an exported function taking an anonymous map, e.g. f: func(m: map<string, list<string>>), bindgen! generates:

pub fn call_f<S: AsContextMut>(&self, store: S, arg0: HashMap<&str, &[String]>) -> ...

while for a named type named = map<string, string> it generates call_g(.., arg0: &Named).

The anonymous form means a caller holding a HashMap<String, Vec<String>> has to build (and hash) a second map of references just to make the call, and it's inconsistent with both named maps and lists (which are &[T]). Generating &HashMap<K, V> with owned keys and values, the way lists are handled, would fix both. Since this changes generated signatures it seems worth settling before map is enabled by default.