Automatically validating Actors

• AActor::CheckForErrors can be overridden to check Actors placed in levels. It runs during MapCheck. Use FMessageLog to log data from it. This also runs if using the Validate Assets action, but runs against the CDO in that case and is likely to not have components available.
• See also editor validators https://dev.epicgames.com/documentation/en-us/unreal-engine/data-validation-in-unreal-engine