Expose playerIndex / DeviceID in GameController framework for Wwise Motion support in Unity

**Is your feature request related to a problem? Please describe.**
We cannot use Wwise Motion on Apple platforms for haptics due to missing `playerIndex` / `DeviceID` exposure in the Apple Unity Plug-ins.

See Wwise Motion [documentation](https://www.audiokinetic.com/en/public-library/2024.1.9_8920/?source=SDK&id=integrating_elements_motion.html) that requires for all Apple platforms to set the `DeviceID` even for single player games. Otherwise Wwise Motion is not playing any haptics / rumble on Apple platforms.

We use it on all other platforms like Windows and consoles. Thus, the need to have that covered to bring also the same experience to Apple platforms.

**Describe the solution you'd like**
Being able to set the `playerIndex` through C# functions / `Get/Set` methods within Unity and then to retrieve the `DeviceID` needed for Wwise Motion.

**Describe alternatives you've considered**
Shipping on Apple platforms without haptics / rumble support.

**Additional context**
Submitted Apple Feedback ID: FB18696265

Beginne damit, das GameController-Framework und die in der Issue verlinkte Dokumentation zu Apple Unity Plug-ins zu lesen, und verfolge anschließend, wie Spielereingaben auf Apple-Plattformen über C# bereitgestellt werden. Die Arbeit ist abgeschlossen, wenn Unity-Aufrufer playerIndex setzen und die von Wwise Motion für Apple-Haptik benötigte DeviceID abrufen können.

Vom Indexierungsmodell aus dem Issue-Text verfasst.