Administration: Unify the date structure in list view and excerpt view.

Both views now show a full date string. Something like `Published 2020/05/27 at 10:25 pm`.

Fixes: #35391.
Props: afercia, ocean90, TimothyBlynJacobs, audrasjb, SergeyBiryukov, joedolson.


Built from https://develop.svn.wordpress.org/trunk@47879


git-svn-id: https://core.svn.wordpress.org/trunk@47653 1a063a9b-81f0-0310-95a4-ce76da25c4cd