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/SyntheticModule.cpp

@@ -53,7 +53,7 @@ ThrowCompletionOr<void> SyntheticModule::link(VM& vm)
     auto& global_object = realm().global_object();
 
     // 3. Let env be NewModuleEnvironment(realm.[[GlobalEnv]]).
-    auto* environment = vm.heap().allocate_without_global_object<ModuleEnvironment>(&realm().global_environment());
+    auto* environment = vm.heap().allocate_without_realm<ModuleEnvironment>(&realm().global_environment());
 
     // 4. Set module.[[Environment]] to env.
     set_environment(environment);