Textinput: added tabindex -1 on clearbuttons

(cherry picked from commit 826ada00f7bbb48784b05ce9376b9746df4dc742)

Closes gh-7155
Fixes gh-6467
Textinput: Add aria-hidden="true" to clear button and test correct markup

Closes gh-7647

(cherry picked from commit 29f036404181c31dc77cab382cd17fb3b103135e)