Change menu items to ARIA role of "menuitemradio" when only one item can be selected

[OwenEdwards]

Description

Change menu items to ARIA role of "menuitemradio" when only one item can be selected can be selected (i.e. in the Captions, Subtitles, Descriptions, Chapters, Audio Tracks, and Rate menus). Fixes #5136.

Specific Changes proposed

Add an option of multiSelectable on MenuItem component; if true, the item is marked as a checkbox (role="menuitemcheckbox"), otherwise the item is marked as a radio button (role="menuitemradio"). All existing menu items, except the Captions Settings Menu, will be marked as radio buttons (the Settings Menu item has role="menuitem"), as will any components which extend the existing components and don't set 'multiSelectable'.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Change has been verified in an actual browser (Chome, Firefox, IE)
  • Unit Tests updated or fixed
• Reviewed by Two Core Contributors

[prozak915]

What's now??

[OwenEdwards]

Also fixes #3663

[gkatsev]

Is the decision regarding Chapters is that it's fine for them to be selectable so no need to keep that issue open?

[OwenEdwards]

@gkatsev yes, that's what we decided. It's fine for Chapters to be selectable, but #5182 needs to be implemented/checked so that the menu doesn't have out-of-date information as the current time progresses.

[gkatsev]

Ah, nice. I thought it already did that? Maybe it went missing at some point.

[OwenEdwards]

I haven't verified it with any SRs, so the Issue is more of a note to check it, and perhaps add some hidden text which clarifies that it's a little more complicated than just radio buttons. We also need to verify that it doesn't announce via an SR when the menu isn't focused/opened, like I noted for other menus in #5172.