Media: Translate a string for the search placeholder.

props alex-ye.
fixes #29448.

Built from https://develop.svn.wordpress.org/trunk@29659


git-svn-id: http://core.svn.wordpress.org/trunk@29433 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media: add a class to the <script> tag for the JSON encoded playlist data so it can be easily selected in WPPlaylistView. Props SergeyBiryukov, fixes #29383
Built from https://develop.svn.wordpress.org/trunk@29660


git-svn-id: http://core.svn.wordpress.org/trunk@29434 1a063a9b-81f0-0310-95a4-ce76da25c4cd