Fix Keyboard events and KeyboardAvoidingView on Android (edge-to-edge)

[zoontek]

Summary:

KeyboardAvoidingView has several issues on Android 15+ and when edgeToEdgeEnabled is set to true on older Android versions:

1. Keyboard events relied on a legacy detection path for Android < 30 (checkForKeyboardEventsLegacy), which used height heuristics (heightDiff > mMinKeyboardHeightDetected) to guess whether the keyboard was visible. This approach is unreliable with edge-to-edge, where the visible display frame and screen dimensions differ from what the heuristic expects.

2. keyboardDidHide reported incorrect screenY values. It used mVisibleViewArea.height(), which in edge-to-edge mode doesn't correspond to the actual screen bottom. This caused KeyboardAvoidingView to compute a non-zero keyboard overlap even after the keyboard was dismissed.

3. KeyboardAvoidingView used _onKeyboardChange for keyboardDidHide on Android, which stores the event instead of nullifying it. After keyboard dismissal, any subsequent onLayout would re-enter _updateBottomIfNecessary with stale coordinates, causing a render loop (especially visible with behavior="height" in edge-to-edge mode, where frame.y shifts slightly on each layout cycle).

This PR:

• Removes checkForKeyboardEventsLegacy and uses WindowInsetsCompat APIs (via AndroidX) for all Android versions, providing reliable keyboard detection in both legacy and edge-to-edge modes.
• Fixes keyboardDidHide to report screenY as mVisibleViewArea.bottom + barInsets.bottom (the actual screen bottom including navigation bars).
• Fixes the Android keyboardDidHide listener in KeyboardAvoidingView to use _onKeyboardHide (which nullifies _keyboardEvent), matching the iOS behavior and breaking the render loop.

Closes #49759

Changelog:

[ANDROID] [FIXED] - Fix KeyboardAvoidingView on Android 15+ / with edgeToEdgeEnabled

Test Plan:

Tested with rn-tester KeyboardAvoidingView example on:

• Android 16 (API 36) (edge-to-edge is enforced)
• Android 14 (API 34) with edgeToEdgeEnabled set to true or false
• Android 7 (API 24) with edgeToEdgeEnabled set to true or false

For each, verified:

• behavior="padding": keyboard open/close adjusts padding correctly
• behavior="position": keyboard open/close translates content correctly
• behavior="height": keyboard open/close works without render loop or glitching
• keyboardDidShow and keyboardDidHide events report correct coordinates

[zoontek]

In order to simplify the codebase here, checkForKeyboardEventsLegacy is removed and checkForKeyboardEvents now uses AndroidX.

[zoontek]

As mVisibleViewArea height doesn't include system UI height, we cannot rely on it when the app is edge-to-edge:

[zoontek]

This solves a crazy render loop (with the UI jumping back and forth) when using KeyboardAvoidingView with behavior="height"