Docs: Add and correct @since docs for a variety of functions and methods.

Props keesiemeijer, chris_dev
Fixes #39343, #39357, #39344
See #39130

Built from https://develop.svn.wordpress.org/trunk@39638


git-svn-id: http://core.svn.wordpress.org/trunk@39578 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -1518,6 +1518,8 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 	 * "Protected: %s", as the REST API communicates the protected status of a post
 	 * in a machine readable format, we remove the "Protected: " prefix.
 	 *
+	 * @since 4.7.0
+	 *
 	 * @return string Protected title format.
 	 */
 	public function protected_title_format() {