land_detector: multicopter ground contact fixes, improvements, and cleanup

- if "landed" and "maybe_landed" states are false then both the "hit_ground" and the "low_thrust" condition need to be true in order to detect landing
 - ground contact MC NAN setpoint workaround
 - ground contact additionally check acceleration setpoint
 - schedule with vehicle_local_position updates (most updates require valid local position)
 - don't allow LNDMC_Z_VEL_MAX to exceed MPC_LAND_SPEED
 - ground contact horizontal movement checks default to failed if estimates aren't available

src/modules/commander/Commander.cpp

@@ -1575,7 +1575,6 @@ Commander::run()
 		/* Update land detector */
 		if (_land_detector_sub.updated()) {
 			_was_landed = _land_detector.landed;
-			bool was_falling = _land_detector.freefall;
 			_land_detector_sub.copy(&_land_detector);
 
 			// Only take actions if armed
@@ -1596,12 +1595,6 @@ Commander::run()
 						_lvel_probation_time_us = _param_com_pos_fs_prob.get() * 1_s;
 					}
 				}
-
-				if (was_falling != _land_detector.freefall) {
-					if (_land_detector.freefall) {
-						mavlink_log_info(&mavlink_log_pub, "Freefall detected");
-					}
-				}
 			}
 		}