REGRESSION: hook_local_actions doesn't use title callback

follow-up to #1908756: Separate Action Links (MENU_LOCAL_ACTION) from hook_menu()

In Drupal 7 if a title callback was specified for a local action is would be used in rendering it in menu_local_tasks()

This menu API feature may not have been used in core, but was used by contrib modules.

In the issue above, the local actions definitions were split out into a separate hook, but it includes a regression since the title callback is no longer used (if it exists) for the given route.

This related issue should use the same resolution for title callbacks: #2004334: Separate Tabs (MENU_LOCAL_TASK) from hook_menu()