GM:NotifyShouldTransmit
Description
Called whenever this entity changes its transmission state for this LocalPlayer, such as exiting or re entering the PVS (Potential Visibility Set).
This is the best place to handle the reset of Entity:SetPredictable, as this would be usually called when the player lags and requests a full packet update.
When the entity stops transmitting, Entity:IsDormant will only return true after this hook.