MDL-63977 Behat: Add generic way to get tag list

lib/behat/behat_base.php

@@ -647,6 +647,16 @@ class behat_base extends Behat\MinkExtension\Context\RawMinkContext {
         return;
     }
 
+    /**
+     * Checks if the current scenario, or its feature, has a specified tag.
+     *
+     * @param string $tag Tag to check
+     * @return bool True if the tag exists in scenario or feature
+     */
+    public function has_tag(string $tag) : bool {
+        return array_key_exists($tag, behat_hooks::get_tags_for_scenario());
+    }
+
     /**
      * Change browser window size.
      *   - small: 640x480