message: PanelHeaderBack: add aria-label; refactor
  clean up markup to get it to match standart lib code
diff: @@ -11,15 +11,18 @@ export type PanelHeaderBackProps = PanelHeaderButtonProps & AdaptivityProps & {
  'aria-label'?: string;
  };
  -const PanelHeaderBack: FunctionComponent<PanelHeaderBackProps> = ({ label, sizeX, ...props }: PanelHeaderButtonProps & AdaptivityProps) => {
  +const PanelHeaderBack: FunctionComponent<PanelHeaderBackProps> = ({ label, sizeX, ...restProps }: PanelHeaderButtonProps & AdaptivityProps) => {
  const platform = usePlatform();
  const showLabel = platform === VKCOM || platform === IOS && sizeX === SizeType.REGULAR;
  - const className = classNames(getClassName('PanelHeaderBack', platform), {
  - 'PanelHeaderBack--has-label': showLabel && !!label,
  - });
  return (
  - <PanelHeaderButton {...props} vkuiClass={className} label={showLabel && label}>
  + <PanelHeaderButton
  + {...restProps}
  + vkuiClass={classNames(getClassName('PanelHeaderBack', platform), {
  + 'PanelHeaderBack--has-label': showLabel && !!label,
  + })}
  + label={showLabel && label}
  + >
  {platform === ANDROID && <Icon28ArrowLeftOutline />}
  {platform === VKCOM && <Icon28ChevronLeftOutline />}
  {platform === IOS && <Icon28ChevronBack />}
  