Conditionally set the the `secure` flag on the test cookie, post password cookie, settings cookies, and comment author cookies depending on whether the front end and/or admin area are served over `https`. Fixes #28427
Built from https://develop.svn.wordpress.org/trunk@28895


git-svn-id: http://core.svn.wordpress.org/trunk@28694 1a063a9b-81f0-0310-95a4-ce76da25c4cd