Accessibility: don't read staff text and other extra info for each note of chord

1) enable a NVDA
2) chord of 2 or more notes
3) add staff text
4) navigate between notes using Alt+left/right

Result: the staff text is read for each note of the chord. Same for lyrics, articulations, and other elements actually attached to the chord or segment and not the note itself.

This is unnecessary and distracting. This information actually doesn't need to be read at all when navigating with Alt+left/right, because it will eventually be hit by the navigation. But it is helpful to hear it when navigating using left/right alone, since that will hit only the notes.

Luckily there is a simple solution: only read the chord info for the top note of the chord. This is the only note hit when using left/right. When using alt+right, the top note is encountered first, so one hears the extra info when you first hit the top note of the chord, then navigation takes you through the other notes, then through the other elements - so the extra info "bookends" the notes. The reverse is true with alt+left - first navigation takes you through the extra elements, then through the lower notes in the chord, and finally the top note which reads the extra info, again giving you the "bookends".

Because this relates to #293300: Optimize screenreader info information during score navigation, I am including my implementation for this in the same PR.