Add selection types to TextInput onChange event (#55043)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55043

This change adds TypeScript/Flow types and RNTester examples for the `selection` data in `TextInput.onChange` event.

This is the JS companion to the native changes that add selection data to the onChange event.

NOTE:selection only represents the cursor location when returned via onChange as this will not be invoked on a pure selection change without text change. We should also add this note to the documentation.

## Why

On the web, text input elements provide `selectionStart` and `selectionEnd` properties that are always accessible during input events. This change exposes the selection data that native now provides, allowing developers to access cursor position during onChange.

## What Changed

1. **Flow Types**: Added optional `selection?: Selection` to `TextInputChangeEventData`
2. **TypeScript Types**: Updated `ReactNativeApi.d.ts` with selection type
3. **RNTester**: Updated examples to display selection in event logs

Changelog:
[General][Added] - TextInput onChange event types now include optional selection data

Reviewed By: cipolleschi, necolas

Differential Revision: D90123294

fbshipit-source-id: 5b575b5c14d23ee53cb0de74b2703673af82513b