Shifts the `title` attribute on `more` and `page-break` placeholder images to `alt`, moves the `title` attribute to `alt` on the `style` and `script` placeholders and replaces the images to differentiate between CSS and JS content. Props sabernhardt, abcd95, joedolson. Fixes #62861. Built from https://develop.svn.wordpress.org/trunk@60007 git-svn-id: http://core.svn.wordpress.org/trunk@59348 1a063a9b-81f0-0310-95a4-ce76da25c4cd