Make first person vehicle turrets follow decoupled camera

Problem:
Vehicle aiming needs to be consistent across view modes and input methods. Right now, first-person aiming with a mouse in vehicles is arbitrarily hindered and feels bad to use. You have to try and match your mouse movement to the turret’s turn rate, or excess input gets dropped. When you lift the mouse to swipe again, the turret stops entirely. This makes it impossible to turn smoothly or quickly in first person compared to using third person view or a controller.

Solution:
Use the same aiming model as third person while in first person: let the camera move freely, and have the turret rotate to center on the view. For balance (especially in hardcore), the periscope doesn't even need full 360-degree free look visibility. Instead you can keep the viewport limited to the turret’s current direction. If the player flicks the mouse faster than the turret can turn, the view moves ahead and the screen goes dark where the scope is out of alignment, then recenters as the turret catches up.