sensors: add baro calibration and cleanup

- sensor_baro.msg use SI (pressure in Pascals)
 - update all barometer drivers to publish directly and remove PX4Barometer helper
 - introduce baro cal (offset) mainly as a mechanism to adjust
relative priority
 - commander: add simple baro cal that sets baro offsets to align with
GPS altitude (if available)
 - create new sensors_status.msg to generalize sensor reporting

src/modules/ekf2/EKF2.cpp

@@ -1511,6 +1511,28 @@ void EKF2::UpdateBaroSample(ekf2_timestamps_s &ekf2_timestamps)
 			perf_count(_msg_missed_air_data_perf);
 		}
 
+		bool reset = false;
+
+		// check if barometer has changed
+		if (airdata.baro_device_id != _device_id_baro) {
+			if (_device_id_baro != 0) {
+				PX4_WARN("%d - baro sensor ID changed %" PRIu32 " -> %" PRIu32, _instance, _device_id_baro, airdata.baro_device_id);
+			}
+
+			reset = true;
+
+		} else if (airdata.calibration_count > _baro_calibration_count) {
+			// existing calibration has changed, reset saved baro bias
+			PX4_DEBUG("%d - baro %" PRIu32 " calibration updated, resetting bias", _instance, _device_id_baro);
+			reset = true;
+		}
+
+		if (reset) {
+			// TODO: reset baro ref and bias estimate?
+			_device_id_baro = airdata.baro_device_id;
+			_baro_calibration_count = airdata.calibration_count;
+		}
+
 		_ekf.set_air_density(airdata.rho);
 
 		_ekf.setBaroData(baroSample{airdata.timestamp_sample, airdata.baro_alt_meter});