REST API: Allow overriding jQuery.ajax calls from within wp-admin

There are now 3 places where we call out to the REST API from within wp-admin.  This commit introduces a small library to allow overriding these calls, centralize nonce-passing logic, and eliminate the need to pass a full REST URL down to client code (this last feature is not yet used and will be explored in a separate ticket).

Fixes #40919.


git-svn-id: https://develop.svn.wordpress.org/trunk@41206 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/media.php

@@ -3437,7 +3437,6 @@ function wp_enqueue_media( $args = array() ) {
 		'captions'  => ! apply_filters( 'disable_captions', '' ),
 		'nonce'     => array(
 			'sendToEditor' => wp_create_nonce( 'media-send-to-editor' ),
-			'wpRestApi'    => wp_create_nonce( 'wp_rest' ),
 		),
 		'post'    => array(
 			'id' => 0,