VPN-7459 part 2: iOS VoiceOver improvements

[mcleinman]

Description

After #11091, QA kicked this back as it still had issues for Messages and Settings. I've made a more general solution, but also have made it iOS-only. Most of the things I'm changing were done by a former engineer who had done a deep dive into Accessibility, and were needed for Android. I'm hesitant to mess with things that could affect other platforms' accessibility - hence the conservative iOS-only for most of this.

In addition to fixing the "tap to select bottom bar buttons" fixes, I've included a few other things that jumped out at me:

• "Sign Out" button was read twice - once for the label, once for the button
• Settings rows were read twice
• VoiceOver didn't share which bottom bar button was currently selected

Reference

VPN-7459

Checklist

• My code follows the style guidelines for this project
• I have not added any packages that contain high risk or unknown licenses (GPL, LGPL, MPL, etc. consult with DevOps if in question)
• I have performed a self review of my own code
• I have commented my code PARTICULARLY in hard to understand areas
• I have added thorough tests where needed