Disabled icons on file picker still get focus resulting in them being read out by screen readers

When tabbing through the icons on the filepicker, you can focus on ones that are disabled. This results in a screen reader reading them out to the user, even though it shouldn't.

As an additional part of this issue, it would be good to look at the alt/title attribute pairing of the icons, and see if there is a way to improve this. Also, the strings used for the tooltips should be escaped using y.html.escape