[iOS] Add hover callbacks to Touchable (#4397)

## Description

The Apple side of `onHoverIn`/`onHoverOut`, covering iOS, tvOS and
macOS. Mirrors the Android state machine, with the pointer sampled from
`UIHoverGestureRecognizer` on iOS, the `NSTrackingArea` on macOS, and
the touch stream during a press.

- `RNGHButtonPressEventDelegate` becomes `RNGHButtonEventDelegate` now
that it carries more than presses.
- The touch-derived path is gated on a press-start latch. Without it a
plain pencil tap on an iPad that doesn't report pencil hover would open
a hover on touch-up that nothing could ever close.
- The pointer type is latched for the duration of a hover — a pencil's
`zOffset` collapses to zero as it approaches contact, which would
otherwise make the hover-out claim a different type than the hover-in.
- tvOS drives hover from focus rather than a pointer, so there's no
sample to report; the payload falls back to the button's centre.

## Test plan

Not covered by the JS tests. Needs an iPad with a trackpad or a
hover-capable pencil, a Mac, and a tvOS device for the focus path.

<details>
<summary>Example code</summary>

```tsx
import React, { useState } from 'react';
import { Pressable, StyleSheet, Text, View } from 'react-native';
import {
  GestureHandlerRootView,
  Touchable,
} from 'react-native-gesture-handler';

export default function Example() {
  const [log, setLog] = useState<string[]>([]);
  const callbacks = (source: string) => ({
    onHoverIn: () => setLog((l) => [`${source} onHoverIn`, ...l]),
    onHoverOut: () => setLog((l) => [`${source} onHoverOut`, ...l]),
    onPressIn: () => setLog((l) => [`${source} onPressIn`, ...l]),
    onPressOut: () => setLog((l) => [`${source} onPressOut`, ...l]),
  });

  return (
    <GestureHandlerRootView style={styles.container}>
      <View style={styles.row}>
        <Touchable style={styles.box} {...callbacks('Touchable')}>
          <Text style={styles.text}>Touchable</Text>
        </Touchable>
        <Pressable style={styles.box} {...callbacks('Pressable')}>
          <Text style={styles.text}>Pressable</Text>
        </Pressable>
      </View>
      {log.slice(0, 12).map((entry, i) => (
        <Text key={i}>{entry}</Text>
      ))}
    </GestureHandlerRootView>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, padding: 24 },
  row: { flexDirection: 'row', gap: 24, marginBottom: 24 },
  box: {
    width: 120,
    height: 120,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: '#6941C6',
  },
  text: { color: 'white' },
});
```

</details>