title: UIBarButtonItem's customView accessibility
body: <p>I've created <code>UIBarButtonItem</code> with <code>customView</code> set to <code>BadgeButton</code> (a <code>UIButton</code> that has badge label added).</p>
  
  <p>I am setting <code>accessibilityIdentifier = "properIDHere"</code> and <code>isAccessibilityElement = true</code>  for both: <code>aBadgeButton</code> and <code>aBadgeButton.badgeLabel</code></p>
  
  <p>When running UITests the badge button is visible and accessible by the ID, but the badgeLabel is not. Do you have ideas why?</p>
  
  <pre><code>final class BadgeButton: MyBaseButton {
     let badgeLabel = UILabel()
  
     override func addSubviews() {
      addSubview(badgeLabel)
     }
  
     override func setupConstraints() {
      badgeLabel.snp.makeConstraints { make in
          make.width.height.equalTo(badgeSize)
          make.centerX.equalToSuperview().offset(badgeXOffset)
          make.centerY.equalToSuperview().offset(badgeYOffset)
      }
  }
  </code></pre>