flight tasks smoothing: refactor param_find -> Param

src/lib/FlightTasks/tasks/FlightTaskManualAltitudeSmooth.cpp

src/lib/FlightTasks/tasks/FlightTaskManualPositionSmooth.cpp

src/lib/FlightTasks/tasks/Utility/ManualSmoothingXY.cpp

src/lib/FlightTasks/tasks/Utility/ManualSmoothingXY.hpp

src/lib/FlightTasks/tasks/Utility/ManualSmoothingZ.cpp

src/lib/FlightTasks/tasks/Utility/ManualSmoothingZ.hpp

src/systemcmds/tests/test_smooth_z.cpp