px4_work_queue: command line status output and shutdown empty queues

* adds a work_queue systemcmd that will bring a tree view of all active work queues and work items
 * WorkQueues now track attached WorkItems and will shutdown when the last WorkItem is detached

src/modules/mc_att_control/mc_att_control_main.cpp

@@ -63,7 +63,7 @@ using namespace matrix;
 
 MulticopterAttitudeControl::MulticopterAttitudeControl() :
 	ModuleParams(nullptr),
-	WorkItem(px4::wq_configurations::rate_ctrl),
+	WorkItem(MODULE_NAME, px4::wq_configurations::rate_ctrl),
 	_loop_perf(perf_alloc(PC_ELAPSED, "mc_att_control"))
 {
 	_vehicle_status.vehicle_type = vehicle_status_s::VEHICLE_TYPE_ROTARY_WING;