px4_work_queue: revert inherited sched attr and run wq:manager and max priority

Setting PTHREAD_EXPLICIT_SCHED was necessary on linux to create WQ threads with priorities relative to max, but unfortunately we can't rely pthread_attr_setinheritsched as it's dependent on system ulimit configuration or running privileged. Instead we can create the wq:manager at the maximum desired priority and allow each WQ thread to have a relative priority.

platforms/common/px4_work_queue/WorkQueueManager.cpp

@@ -270,14 +270,6 @@ WorkQueueManagerRun(int, char **)
 #if defined(ENABLE_LOCKSTEP_SCHEDULER)
 			int ret_setschedpolicy = pthread_attr_setschedpolicy(&attr, SCHED_RR);
 #else
-
-			// don't inherit attributes from parent thread
-			int ret_setinheritsched = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
-
-			if (ret_setinheritsched != 0) {
-				PX4_ERR("failed to set inherit-scheduler attribute PTHREAD_EXPLICIT_SCHED (%i)", ret_setinheritsched);
-			}
-
 			int ret_setschedpolicy = pthread_attr_setschedpolicy(&attr, SCHED_FIFO);
 #endif
 
@@ -327,7 +319,7 @@ WorkQueueManagerStart()
 
 		int task_id = px4_task_spawn_cmd("wq:manager",
 						 SCHED_DEFAULT,
-						 PX4_WQ_HP_BASE,
+						 SCHED_PRIORITY_MAX,
 						 1280,
 						 (px4_main_t)&WorkQueueManagerRun,
 						 nullptr);