Refactor RZInput: Simplify and Modularize Input System for Multi-Device Support

[Pikachuxxxx]

The current RZInput design uses a singleton-based virtual interface that delegates to platform-specific implementations (e.g., GLFW), which is cumbersome to maintain and extend. especially as we start supporting more complex HID devices like PS5 DualSense controllers, Xbox gamepads, or other non-standard input devices.

we can use static functinos and compile the necessary backend per platform, we don't need dynamic switching and remove the virtual interfaces, this is similar to how RZFileSystem is implemented.