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.h

@@ -46,7 +46,7 @@ public:
     virtual void initialize(GlobalObject&) override;
     virtual ~PromiseResolvingElementFunction() override = default;
 
-    virtual Value call() override;
+    virtual ThrowCompletionOr<Value> call() override;
 
 protected:
     explicit PromiseResolvingElementFunction(size_t, PromiseValueList&, PromiseCapability, RemainingElements&, Object& prototype);