Prevent each call to `get_post()` triggering a seperate database query by priming the cache of each comment's post in the REST API's comments endpoint. Props spacedmonkey, timothyblynjacobs. Fixes #56272. Built from https://develop.svn.wordpress.org/trunk@53772 git-svn-id: http://core.svn.wordpress.org/trunk@53331 1a063a9b-81f0-0310-95a4-ce76da25c4cd