AC-659: Create phpcs static check for ModuleXMLTest

Author: svera

Magento2/Sniffs/Legacy/ModuleXMLSniff.php

@@ -40,7 +40,8 @@ public function process(File $phpcsFile, $stackPtr)
         }
 
         // We need to format the incoming XML to avoid tags split into several lines. In that case, PHP's DOMElement
-        // returns the position of the closing /> as the position of the tag.
+        // returns the position of the closing /> as the position of the tag, and we need the position of <module
+        // instead, as it is the one we compare with $stackPtr later on.
         $xml = simplexml_load_string($this->getFormattedXML($phpcsFile));
         if ($xml === false) {
             $phpcsFile->addError(