[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

common/shared_tasks.h

@@ -28,6 +28,7 @@
 #define ServerOP_SharedTaskPlayerList               0x0313 // zone -> world /taskplayerlist command
 #define ServerOP_SharedTaskMemberChange             0x0314 // world -> zone. Send shared task single member added/removed (client also handles message)
 #define ServerOP_SharedTaskKickPlayers              0x0315 // zone -> world /kickplayers task
+#define ServerOP_SharedTaskLock                     0x0316 // zone -> world
 
 enum class SharedTaskRequestGroupType {
 	Solo = 0,
@@ -105,6 +106,8 @@ struct SharedTaskActivityStateEntry {
 	uint32 max_done_count; // goalcount
 	uint32 updated_time;
 	uint32 completed_time;
+	int    step;
+	bool   optional;
 };
 
 struct ServerSharedTaskActivityUpdate_Struct {
@@ -162,6 +165,12 @@ struct ServerSharedTaskKickPlayers_Struct {
 	uint32 task_id;
 };
 
+struct ServerSharedTaskLock_Struct {
+	uint32 source_character_id;
+	uint32 task_id;
+	bool   lock;
+};
+
 class SharedTask {
 public:
 	// used in both zone and world validation