actuator: add support for MAV_CMD_DO_SET_ACTUATOR

Adds support for using the MAVLink command MAV_CMD_DO_SET_ACTUATOR to
update the actuator values on control group 3 aux{1, 2, 3}. A simple
deconfliction with rc_update is implemented: when a MAVLink command is
sent, RC is disabled for that channel until a major stick movement is
detected.

src/modules/rc_update/rc_update.h

@@ -161,6 +161,7 @@ private:
 	uORB::SubscriptionInterval _parameter_update_sub{ORB_ID(parameter_update), 1_s};
 
 	uORB::Subscription _rc_parameter_map_sub{ORB_ID(rc_parameter_map)};
+	uORB::Subscription _actuator_controls_3_sub{ORB_ID(actuator_controls_3)};
 
 	uORB::Publication<rc_channels_s> _rc_channels_pub{ORB_ID(rc_channels)};
 	uORB::PublicationMulti<manual_control_setpoint_s> _manual_control_setpoint_pub{ORB_ID(manual_control_setpoint)};
@@ -179,6 +180,8 @@ private:
 	hrt_abstime _last_timestamp_signal{0};
 
 	uint16_t _rc_values_previous[RC_MAX_CHAN_COUNT] {};
+	float _last_manual_control_setpoint[3] {};
+	bool _aux_already_active[3] = {false, false, false};
 
 	uint8_t _channel_count_previous{0};
 	uint8_t _input_source_previous{input_rc_s::RC_INPUT_SOURCE_UNKNOWN};