Consolidate handling of <object>, <audio> and <video> in wpautop() and add...

Consolidate handling of <object>, <audio> and <video> in wpautop() and add unit tests for them. Part props wonderboymusic, see #26864
Built from https://develop.svn.wordpress.org/trunk@27094


git-svn-id: https://core.svn.wordpress.org/trunk@26966 1a063a9b-81f0-0310-95a4-ce76da25c4cd