Fixed: actors that didn't need to respawn upon resetting the map didn't trigger GAMEEVENT_ACTOR_SPAWNED.

This addresses: https://zandronum.com/tracker/view.php?id=4211

Actors that didn't need to be respawned upon resetting the map never executed AActor::PostBeginPlay and wouldn't trigger GAMEEVENT_ACTOR_SPAWNED normally. I separated the code that handles the spawn event into a new function, that also gets called in GAME_ResetMap when handling actors that are untouched and don't respawn.