Include option to use ViewTarget's location when determining relevancy

When determining relevancy for an actor based on distance, the location of the player's view point is always used if it is available, rather than the location of the view target (see FNetViewer and APlayerController::GetPlayerViewPoint). Because this is usually the location of the player's camera, this can cause difficulty with accurately determining relevancy in projects where the player's pawn is far away from its camera (e.g. a top down view).
An option to default to the view target's location would allow projects to choose whether to use the location of either the camera or the pawn when determining relevancy.

Create a replicated actor with a short net cull distance squared.
Create a pawn with a camera that is far away from the actual character.
When approaching the actor's location, observe that relevancy is determined by the distance to the camera rather than the character, leading to the actor becoming relevant at an unexpected time or not at all depending on the camera's position.