Make LandingTargetEstimator a lib and run on work_queue

Currently only precision landing is using the
LandingTargetEstimator and it is a waste to have it
running in the background all the time. With this change
the estimator is only started once the precision landing
flight task is activated, and stopped when the flight
task is deactivated.

src/modules/flight_mode_manager/tasks/AutoPrecisionLanding/CMakeLists.txt

@@ -32,8 +32,16 @@
 ############################################################################
 
 px4_add_library(FlightTaskAutoPrecisionLanding
-FlightTaskAutoPrecisionLanding.cpp
+	FlightTaskAutoPrecisionLanding.cpp
 )
 
-target_link_libraries(FlightTaskAutoPrecisionLanding PUBLIC FlightTaskAuto)
-target_include_directories(FlightTaskAutoPrecisionLanding PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+target_link_libraries(FlightTaskAutoPrecisionLanding
+	PUBLIC
+	FlightTaskAuto
+	LandingTargetEstimator
+)
+
+target_include_directories(FlightTaskAutoPrecisionLanding
+	PUBLIC
+	${CMAKE_CURRENT_SOURCE_DIR}
+)

src/modules/flight_mode_manager/tasks/AutoPrecisionLanding/FlightTaskAutoPrecisionLanding.cpp

@@ -45,6 +45,16 @@
 
 static constexpr const char *LOST_TARGET_ERROR_MESSAGE = "Lost landing target while landing";
 
+FlightTaskAutoPrecisionLanding::FlightTaskAutoPrecisionLanding()
+{
+	_landing_target_estimator.Start();
+}
+
+FlightTaskAutoPrecisionLanding::~FlightTaskAutoPrecisionLanding()
+{
+	_landing_target_estimator.Stop();
+}
+
 bool FlightTaskAutoPrecisionLanding::activate(const trajectory_setpoint_s &last_setpoint)
 {
 	bool ret = FlightTask::activate(last_setpoint);

src/modules/flight_mode_manager/tasks/AutoPrecisionLanding/FlightTaskAutoPrecisionLanding.hpp

@@ -45,6 +45,7 @@
 
 #include <matrix/math.hpp>
 #include <mathlib/mathlib.h>
+#include <landing_target_estimator/LandingTargetEstimator.h>
 #include <lib/geo/geo.h>
 #include <px4_platform_common/module_params.h>
 #include <uORB/Subscription.hpp>
@@ -74,8 +75,8 @@ enum class PrecLandMode {
 class FlightTaskAutoPrecisionLanding : public FlightTaskAuto
 {
 public:
-	FlightTaskAutoPrecisionLanding() = default;
-	virtual ~FlightTaskAutoPrecisionLanding() = default;
+	FlightTaskAutoPrecisionLanding();
+	~FlightTaskAutoPrecisionLanding();
 
 	bool activate(const trajectory_setpoint_s &last_setpoint) override;
 
@@ -104,6 +105,8 @@ private:
 	bool check_state_conditions(PrecLandState state);
 	void slewrate(float &sp_x, float &sp_y);
 
+	landing_target_estimator::LandingTargetEstimator _landing_target_estimator;
+
 	landing_target_pose_s _target_pose{}; /**< precision landing target position */
 
 	uORB::Subscription _target_pose_sub{ORB_ID(landing_target_pose)};