Replace the legacy wpe-android view-backend with the new WPE Platform API,
providing a cleaner integration with WebKit's rendering pipeline.

New implementations:
- WPEDisplayAndroid: Android-specific WPEDisplay
- WPEToplevelAndroid: Window/toplevel management
- WPEViewAndroid: View with buffer handling via AHardwareBuffer
- WPEInputMethodContextAndroid: Input method context

Key changes:
- RendererSurfaceControl uses WPEBuffer directly instead of WPEAndroidBuffer
- Connect fundamental WebKit signals for navigation, loading, and UI

Add full keyboard support for web content using WPE's input method context:

- AndroidKeyMap.h: Maps Android keycodes to XKB keysyms
- WPEInputConnection: Android InputConnection for soft keyboard
- Support for text composition, deletion, and hardware key events

The input method context integrates with WPE's focus tracking to
show/hide the soft keyboard when input fields gain or lose focus.

WebKit notifications for media playback and capture state changes:

- notify::is-playing-audio: Track when audio starts/stops playing
- notify::is-muted: Track mute state changes
- notify::camera-capture-state: Track camera capture activity
- notify::microphone-capture-state: Track microphone capture activity
- notify::display-capture-state: Track screen sharing activity

Navigation improvements:
- Update URL bar when page URI changes
- Handle device back button to navigate browser history
- Default to HTTPS when scheme is not specified
- Clear focus from URL bar after navigation

UI improvements:
- Move progress bar above toolbar
- Update UI style and colors