LibJS: Clarify Object (base class) construction somewhat

Divide the Object constructor into three variants:

- The regular one (takes an Object& prototype)
- One for use by GlobalObject
- One for use by objects without a prototype (e.g ObjectPrototype)

Libraries/LibJS/Runtime/BigIntObject.cpp

@@ -37,7 +37,7 @@ BigIntObject* BigIntObject::create(GlobalObject& global_object, BigInt& bigint)
 }
 
 BigIntObject::BigIntObject(BigInt& bigint, Object& prototype)
-    : Object(&prototype)
+    : Object(prototype)
     , m_bigint(bigint)
 {
 }