Add support for PHP 8 union types

Problem/Motivation

  /**
   * A mock of the `datetime.time` service.
   *
   * @var \Drupal\Component\Datetime\TimeInterface|\PHPUnit\Framework\MockObject\MockObject
   */
  protected TimeInterface|MockObject $datetime;

The above is valid PHP8+ code however Coder generates `Missing member variable doc comment (Drupal.Commenting.VariableComment.Missing)` in case the member has a union types spec.

Steps to reproduce

class Test {
  protected int|float $var;
}

Analyze the above snippet with Coder.