Android audio initialization via ContextUtils; pipeline options for remote data tracks

Features

• Introduce pipeline options for remote data tracks, support multiple in-flight frames.

feat: add Android application context initialization for PlatformAudio support.

Android requires ContextUtils.initialize(applicationContext) before WebRTC audio components can be created. This change:

• Adds livekit_ffi_initialize_android_context() C FFI function for Unity and other FFI consumers
• Uses CreateAndroidAudioDeviceModule() instead of generic CreateAudioDeviceModule() on Android
• Handles empty device GUIDs on Android (falls back to index 0)
• Documents Android-specific limitations: single default device, no app-level device selection

Platform notes:

• Android device enumeration returns only one "default" device with empty name/GUID
• Audio routing (speaker/earpiece/Bluetooth) is controlled by Android's AudioManager, not WebRTC

Fixes

• Filter internal data streams out of livekit-ffi interface - #1112 (@1egoman)