MDL-76398 behat: broader action menu partial matching by element.

For action menu elements whose trigger element isn't plain text
(e.g. a pix icon), we should be able to match via the title of
that element.

lib/behat/classes/partial_named_selector.php

@@ -145,7 +145,7 @@ XPATH
     descendant::*[
         contains(concat(' ', normalize-space(@class), ' '), ' dropdown-toggle ')
             and
-        contains(normalize-space(.), %locator%)
+        (contains(normalize-space(.), %locator%) or descendant::*[%titleMatch%])
     ]
 ]
 XPATH