LibJS+LibWeb: Replace GlobalObject with Realm in Heap::allocate<T>()

This is a continuation of the previous three commits.

Now that create() receives the allocating realm, we can simply forward
that to allocate(), which accounts for the majority of these changes.
Additionally, we can get rid of the realm_from_global_object() in one
place, with one more remaining in VM::throw_completion().

Userland/Libraries/LibJS/Module.cpp

@@ -87,6 +87,8 @@ ThrowCompletionOr<Object*> Module::get_module_namespace(VM& vm)
 // 10.4.6.12 ModuleNamespaceCreate ( module, exports ), https://tc39.es/ecma262/#sec-modulenamespacecreate
 Object* Module::module_namespace_create(VM& vm, Vector<FlyString> unambiguous_names)
 {
+    auto& realm = this->realm();
+
     // 1. Assert: module.[[Namespace]] is empty.
     VERIFY(m_namespace.is_null());
 
@@ -97,7 +99,7 @@ Object* Module::module_namespace_create(VM& vm, Vector<FlyString> unambiguous_na
     // 6. Let sortedExports be a List whose elements are the elements of exports ordered as if an Array of the same values had been sorted using %Array.prototype.sort% using undefined as comparefn.
     // 7. Set M.[[Exports]] to sortedExports.
     // 8. Create own properties of M corresponding to the definitions in 28.3.
-    Object* module_namespace = vm.heap().allocate<ModuleNamespaceObject>(realm().global_object(), realm(), this, move(unambiguous_names));
+    Object* module_namespace = vm.heap().allocate<ModuleNamespaceObject>(realm, realm, this, move(unambiguous_names));
 
     // 9. Set module.[[Namespace]] to M.
     m_namespace = make_handle(module_namespace);