[Fix]: use variable value in prop type field defined by a variable

[jzabala]

Use the variable value in cases where the type is given by a variable. Example:

const firstType = PropTypes.shape({
  id: PropTypes.number,
});
class ComponentX extends React.Component {
  static propTypes = {
    first: firstType.isRequired, // resolve to `first: PropTypes.shape({ id: PropTypes.number }).isRequired`
  };
  render() {
    return (
      <div>
        {/*Correctly validates that first.name is not defined in propTypes.*/}
        <div>Counter = {this.props.first.name}</div>
      </div>
    );
  }
}

Fixes #2236