Fix a race condition in classic edit toolbar setup

mediawiki.action.edit used to call mw.toolbar.init on its own during DOMReady -- this required that the module already be loaded *before* DOMReady, *and* that it be fully loaded before the immedate-execution code that sets up the default toolbar items (output from EditPage.php).
This failed since we've gone fully async in the bottom-loading items, and could result in failed calls to mw.toolbar.addButton.

Wrapped those immediate calls in a mediawiki.loader.using call to ensure they're run after the module is loaded, and moved the mw.toolbar.init call into that section so we guarantee it gets run first.

includes/EditPage.php

@@ -2671,7 +2671,7 @@ HTML
 			)
 		);
 
-		$script = '';
+		$script = 'mw.loader.using("mediawiki.action.edit", function() {';
 		foreach ( $toolarray as $tool ) {
 			if ( !$tool ) {
 				continue;
@@ -2692,6 +2692,14 @@ HTML
 
 			$script .= Xml::encodeJsCall( 'mw.toolbar.addButton', $params );
 		}
+		
+		// This used to be called on DOMReady from mediawiki.action.edit, which
+		// ended up causing race conditions with the setup code above.
+		$script .= "\n" .
+			"// Create button bar\n" .
+			"$(function() { mw.toolbar.init(); } );\n";
+
+		$script .= '});';
 		$wgOut->addScript( Html::inlineScript( ResourceLoader::makeLoaderConditionalScript( $script ) ) );
 
 		$toolbar = '<div id="toolbar"></div>';

resources/mediawiki.action/mediawiki.action.edit.js

@@ -82,9 +82,6 @@
 		};
 		scrollEditBox();
 
-		// Create button bar
-		mw.toolbar.init();
-
 		$( 'textarea, input:text' ).focus( function() {
 			currentFocused = $(this);
 		});