TinyMCE: improve the previews for embedded WordPress posts:

- Add option to force a sandbox iframe in wpview.
- Use it to show the embedded post preview.
- Remove the deprecated `wpembed` plugin.js

Fixes #39513.
Built from https://develop.svn.wordpress.org/trunk@40019


git-svn-id: http://core.svn.wordpress.org/trunk@39956 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/tinymce/plugins/wpembed/plugin.js

@@ -1,17 +0,0 @@
-(function ( tinymce ) {
-	'use strict';
-
-	tinymce.PluginManager.add( 'wpembed', function ( editor, url ) {
-		editor.on( 'init', function () {
-			var scriptId = editor.dom.uniqueId();
-
-			var scriptElm = editor.dom.create( 'script', {
-				id: scriptId,
-				type: 'text/javascript',
-				src: url + '/../../../wp-embed.js'
-			} );
-
-			editor.getDoc().getElementsByTagName( 'head' )[ 0 ].appendChild( scriptElm );
-		} );
-	} );
-})( window.tinymce );

wp-includes/js/tinymce/plugins/wpembed/plugin.min.js

@@ -1 +0,0 @@
-!function(a){"use strict";a.PluginManager.add("wpembed",function(a,b){a.on("init",function(){var c=a.dom.uniqueId(),d=a.dom.create("script",{id:c,type:"text/javascript",src:b+"/../../../wp-embed.js"});a.getDoc().getElementsByTagName("head")[0].appendChild(d)})})}(window.tinymce);