LibJS: Convert NativeFunction::{call,construct}() to ThrowCompletionOr

Both at the same time because many of them call construct() in call()
and I'm not keen on adding a bunch of temporary plumbing to turn
exceptions into throw completions.
Also changes the return value of construct() to Object* instead of Value
as it always needs to return an object; allowing an arbitrary Value is a
massive foot gun.

Userland/Libraries/LibJS/Runtime/PromiseResolvingElementFunctions.cpp

@@ -28,7 +28,7 @@ void PromiseResolvingElementFunction::initialize(GlobalObject& global_object)
     define_direct_property(vm().names.length, Value(1), Attribute::Configurable);
 }
 
-Value PromiseResolvingElementFunction::call()
+ThrowCompletionOr<Value> PromiseResolvingElementFunction::call()
 {
     if (m_already_called)
         return js_undefined();