Mark CanRestartPlayer in PlayerController as BlueprintCallable

In blueprint you can override a game mode’s “CanRestartPlayer”, and by default, this calls a PlayerController’s CanRestartPlayer. A PC’s CanRestartPlayer cannot be called in Blueprint however, and its doing some nice checks in C++ that are also not possible in Blueprint. It would be nice if PC’s CanRestartPlayer is either a BlueprintNativeEvent or a BlueprintCallable function so that we can override a game mode’s CanRestartPlayer without losing functionality.