LibJS+LibWeb: Reduce use of GlobalObject as an intermediary

- Prefer VM::current_realm() over GlobalObject::associated_realm()
- Prefer VM::heap() over GlobalObject::heap()
- Prefer Cell::vm() over Cell::global_object()
- Prefer Wrapper::vm() over Wrapper::global_object()
- Inline Realm::global_object() calls used to access intrinsics as they
  will later perform a direct lookup without going through the global
  object

Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp

@@ -324,7 +324,7 @@ JS::GlobalObject& current_global_object()
 JS::Realm& relevant_realm(JS::Object const& object)
 {
     // The relevant Realm for a platform object is the value of its [[Realm]] field.
-    return *object.global_object().associated_realm();
+    return object.shape().realm();
 }
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#relevant-settings-object