Media:

* Make attachment focus styles more obvious, particularly for already selected items.
* Fix styling for the selection set attachments.
* Remove some CSS cruft.

fixes #28822.

Built from https://develop.svn.wordpress.org/trunk@29607


git-svn-id: http://core.svn.wordpress.org/trunk@29381 1a063a9b-81f0-0310-95a4-ce76da25c4cd