LPE land bug fix and switch to fusion bit mask.

posix-configs/SITL/init/lpe/iris_opt_flow

.../local_position_estimator/BlockLocalPositionEstimator.cpp

.../local_position_estimator/BlockLocalPositionEstimator.hpp

src/modules/local_position_estimator/params.c

src/modules/local_position_estimator/sensors/baro.cpp

src/modules/local_position_estimator/sensors/flow.cpp

src/modules/local_position_estimator/sensors/gps.cpp

src/modules/local_position_estimator/sensors/land.cpp

src/modules/local_position_estimator/sensors/lidar.cpp

src/modules/local_position_estimator/sensors/mocap.cpp

src/modules/local_position_estimator/sensors/sonar.cpp

src/modules/local_position_estimator/sensors/vision.cpp