Clear pending timers on unmount in StatefulPressable (#4413)

## Description

The stateful Pressable engine keeps four pending timers -
`longPressTimeoutRef`, `pressDelayTimeoutRef`, `hoverInTimeout` and
`hoverOutTimeout` - but never clears them on unmount. If the component
unmounts while one is pending, the scheduled callback still fires
(`onPressIn` / `onLongPress` / `onHoverIn` / `onHoverOut`, plus a
`setState`), acting on a torn-down component.

This adds a cleanup effect that clears all four on unmount, matching the
cleanup the Touchable-based engine already has.

Follow-up to #4411, flagged by CodeRabbit.

## Test plan

Existing v3 suite passes (`yarn test` in
`packages/react-native-gesture-handler`). No behavior change while
mounted — the effect only cancels timers that would otherwise fire after
unmount.