- Replace NULL uses in new code with nullptr
- Fix wrong (accumulated) load time log when loading calendar invites
- Make Creature::CanRegenerateHealth const as its just a getter
- Mark OnlyOnceAreaTriggerScript::OnTrigger as final in case someone wants to override that (you are supposed to use protected _OnTrigger hook)
(cherry picked from commit 78a1c687a25d91dd6b13251f28d03ec6a0a49b8a)