[Shared Tasks] Implement Activity Locking (#2339)

* Add shared task element locking

This adds the `lock_activity_id` field to the tasks table which will
automatically lock a shared task when that element becomes active.

A method was added to world analogous to zone's UnlockActivities to
determine when an activity is active with respect to task steps.

Also adds quest apis to manually lock or unlock a client's shared task

* Add comment

utils/sql/git/required/2022_07_13_task_lock_activity.sql

@@ -0,0 +1,2 @@
+ALTER TABLE `tasks`
+  ADD COLUMN `lock_activity_id` INT NOT NULL DEFAULT '-1' AFTER `request_timer_seconds`;