Migrate a few more var initializations from the Mavlink class constructor list to the respective declarations.

Whitespace formatting in mavlink_main.cpp/h and begin work of some variable initialization at declaration in mavlink_main.h.

Delete unnecessary #includes from mavlink_main.cpp and relocate a few #defines to mavlink_main.h for future variable initialization work.

Add const specifier to remaining methods utilizing mavlink_message_t and similar message pointer types.

Cut case MAVLINK_MSG_ID_VISION_POSITION_ESTIMATE content and paste into handle_message_vision_position_estimate() method. Add const specifier to publish_odometry_topic() method.

Refactor set_publish() logic so that a default false value is not (re)set each loop in simulator_mapvlink.cpp and provide a default argument to set_publish() in simulator.h.

Create Simulator::set_publish() method and Simulator::_publish member variable to allow redefinition of the Simulator::handle_message() prototype to match MavlinkReceiver::handle_message().

 - fixes #11317

The simulator had hardcoded component ID and system ID (sysID was 0), ignoring what was set up in the params MAV_SYS_ID and MAV_COMP_ID. This caused an issue with multi-vehicle simulations that that rely on sysID to identify the vehicles.

Signed-off-by: Gabriel Moreno <gabrielm@cs.cmu.edu>

 - support range based for loops
 - add remove() method to remove a node
 - add clear() to empty entire list and delete nodes
 - add empty() helper

Except for the lower end with disabled airmode.

Otherwise the rate controller would disable the integrals, which can lead
to severe tracking loss in acro.
It is noticeable when flying in FPV, e.g. simply when throttling straight
up.

Relevant part in the rate controller:
https://github.com/PX4/Firmware/blob/master/src/modules/mc_att_control/mc_att_control_main.cpp#L702

Cut case MAVLINK_MSG_ID_HIL_STATE_QUATERNION content and paste into handle_message_hil_state_quaternion() method.

Cut case MAVLINK_MSG_ID_HIL_OPTICAL_FLOW content and paste into handle_message_hil_optical_flow() method.

Cut case MAVLINK_MSG_ID_DISTANCE_SENSOR content and paste into handle_message_distance_sensor() method.

Cut case MAVLINK_MSG_ID_LANDING_TARGET content and paste into handle_message_landing_target() method.

mission_feasibility_checker: takeoff: add a different log message when there's a takeoff item but it's not the first waypoint

mission_feasibility_checker: takeoff: accept mission when takeoff is not the first item but the previous items are not waypoints

navigator: mission feasibility checker: check for a takeoff waypoint on mission on specific conditions