[v2] Use consistent children syntax in React documentation and examples

The React documentation and examples should use one consistent style for passing children. The proposed convention is to use JSX children between a component's tags instead of passing them through the children prop.

This convention should be applied consistently across:

• the documentation
• the examples.

A consistent style would make the material easier to scan and prevent examples from switching between equivalent forms without a clear reason.

Optionally, the documentation could include a hidden hint explaining that children={} and JSX children are semantically equivalent. The hint could also mention that ESLint can be configured to report inconsistent usage.

Start by locating the React documentation and examples, then search them for uses of the children prop and JSX children syntax. Update the applicable material to consistently use JSX children between component tags, and consider the optional hidden equivalence and ESLint hint. Done means the React documentation and examples no longer switch styles without a clear reason.