For accessibility, all interactive controls must be operable from the keyboard. Replaces `<div>`s used as UI controls with buttons. Groups some logically-related form elements. Fixes #28864. Built from https://develop.svn.wordpress.org/trunk@36223 git-svn-id: http://core.svn.wordpress.org/trunk@36190 1a063a9b-81f0-0310-95a4-ce76da25c4cd