General: Remove noopener from links opening in a new tab.

Removes the automatic addition of `rel="noopener noreferrer"` from links targeting a new tab or window, `target='_blank'`. Since this was introduced, supported browsers have changed their security policies and no longer allow the opened link to have JavaScript access to the previous tab.

Deprecates:

* `wp_targeted_link_rel()`
* `wp_targeted_link_rel_callback()`
* `wp_init_targeted_link_rel_filters()`: converted to a noop function
* `wp_remove_targeted_link_rel_filters()`: converted to a noop function

The deprecated functions are retained in `formatting.php` as in `SHORTINIT` mode the file is included while `deprecated.php` is not.

This also removes the `noopener` from links hard coded within the WordPress dashboard linking to documentation and other resources.

Props audrasjb, azaozz, dhruval04, dorzki, neo2k23, presskopp, sabernhardt, swissspidy, tobiasbg.
Fixes #53843.

Built from https://develop.svn.wordpress.org/trunk@59120


git-svn-id: http://core.svn.wordpress.org/trunk@58516 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/media.php

@@ -3243,7 +3243,7 @@ function edit_form_image_editor( $post ) {
 			__( '<a href="%1$s" %2$s>Learn how to describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
 			/* translators: Localized tutorial, if one exists. W3C Web Accessibility Initiative link has list of existing translations. */
 			esc_url( __( 'https://www.w3.org/WAI/tutorials/images/decision-tree/' ) ),
-			'target="_blank" rel="noopener"',
+			'target="_blank"',
 			sprintf(
 				'<span class="screen-reader-text"> %s</span>',
 				/* translators: Hidden accessibility text. */