sensors: move voting into sensors module

- voting is now at a central place instead of duplicated within the
  estimators
  -> this also means that estimators that did not do voting so far,
     now have voting, like ekf2
- estimators requiring more than that can still subscribe to the raw
  sensors
- allows sensors_combined to be 3 times smaller
  - reduces logger, memcpy (cache) & RAM overhead
- all modules requiring only 1 or 2 sensor values now automatically get
  the voted result
- this also adds voting to baro

src/modules/local_position_estimator/sensors/baro.cpp

@@ -41,7 +41,7 @@ int BlockLocalPositionEstimator::baroMeasure(Vector<float, n_y_baro> &y)
 {
 	//measure
 	y.setZero();
-	y(0) = _sub_sensor.get().baro_alt_meter[0];
+	y(0) = _sub_sensor.get().baro_alt_meter;
 	_baroStats.update(y);
 	_time_last_baro = _timeStamp;
 	return OK;