LibJS: Remove Object(Object& prototype) footgun

This constructor was easily confused with a copy constructor, and it was
possible to accidentally copy-construct Objects in at least one way that
we dicovered (via generic ThrowCompletionOr construction).

This patch adds a mandatory ConstructWithPrototypeTag parameter to the
constructor to disambiguate it.

Userland/Libraries/LibJS/Runtime/StringObject.cpp

@@ -21,7 +21,7 @@ NonnullGCPtr<StringObject> StringObject::create(Realm& realm, PrimitiveString& p
 }
 
 StringObject::StringObject(PrimitiveString& string, Object& prototype)
-    : Object(prototype)
+    : Object(ConstructWithPrototypeTag::Tag, prototype)
     , m_string(string)
 {
 }