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.

Needed a clear scope inside a case for irlock_reports.

In 5bb9babc I made MAVLink send a
rounded up integer instead of rounded down. This makes sense in practice
because the low battery reactions happen exactly when the reported number
switches in the UI. But here we want to provoke an exact 50% in the UI so
we stop counting at 49.9%, it get's rounded up and we see the expected
result.

In 3e6e1f5c the simulated battery
percentage was reversed. I'm assuming because of the possibly
missleading variable name. Now I'm fixing it by switching the
maximum and minimum voltage such that the name is not misleading anymore
but it still works as expected.

It turns out that `sendto` does not work for TCP on Cygwin-Windows,
instead we need to use `send`. This required some refactoring since we
need to have the internet protocol and the port stored as a member
variable.

This should fix that lockstep SITL simulation was not working on
Windows.

It turns out the noise of the airspeed depends on the least significant
bit of time which is now always 0 because time is quite regular with
lockstep. Therefore, we need a better source for the randomness. I chose
to use the sign of the y-gyro and it seems to work.

This is not suposed to ever trigger anyway.

When `connect()` fails, the state of the socket is unspecified and we
need to close the it and create it again.

It turns out retrying connect worked on Linux but it didn't on macOS.

Without setting the device_id, the preflight checks fail because the
calibration is not found.

This adds the option to connect over UDP or TCP for mavlink to the
SITL simulator.

Also, this includes a bunch of general cleanup and refactoring of the
simulator interface code. For instance sending of mavlink messages was
put into separate functions and unneccessary comments were removed.

Also, this now sets the timestamp sent by the SITL simulator in the
HIL_SENSOR message in order to enable lockstep.

This integrates the lockstep_scheduler, so that the system time is set
by the mavlink HIL_SENSOR message.

This means that the speed factor is removed and the speed is entirely
given by the simulator.

This is a step towards isolating time from the system.

- this ensures that the MAV_TYPE parameter is always updated
- previously it could happen that the simulator module was using a wrong
MAV_TYPE value because it only read the parameter value at initialisation

Signed-off-by: Roman <bapstroman@gmail.com>