Improve solution for Mobile VoiceOver

[brent-phet]

In #1736, we decided to remove the current code which enabled iOS VoiceOver and Mobile VoiceOver, in general. Therefore, we need to explore new design patterns to support this features in the future.

[brent-phet]

Per JG, descriptions would still remain after resolve #1736. TS recommends using gestures + voicing over iOS VoiceOver in terms of value.