Keyboard shortcuts: A11Y fixes cherry pick

* Letters are no more announced as capitals
* Focus now moves into the function key buttons (images)
* The keyboard shortcuts are not being verbalized individually
but instead the whole group is now verbalized in one go.

Bug: 29267887
Bug: 29259734
Bug: 29260915
Change-Id: If9370fa9a6eef0e412285ca73794c6d72cdadd15