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

まず GameController フレームワークと issue にリンクされている Apple Unity Plug-ins のドキュメントを読み、次に Apple プラットフォームでプレイヤー入力が C# を通じてどのように公開されているかを追跡します。Unity の呼び出し元が playerIndex を設定し、Apple のハプティクス用に Wwise Motion が必要とする DeviceID を取得できるようになれば、作業は完了です。

索引モデルが issue の本文から書いたものです。