Common - Add loading of dead units into vehicles

[Dystopian]

When merged this pull request will:

• add ability to load dead units into vehicles;
• allow loading while carrying and via medical interaction;
• improve vehicle selection in fnc_nearestVehiclesFreeSeat (ignore dead, locked, flipped, and simulation-disabled vehicles);
• replace distance checks with fnc_getInteractionDistance in dragging functions and reduce max load distance from 5 to 2.

The implementation uses moveInAny. To target specific seats, temporary local units are spawned to probe seat positions.

The distance check was adjusted because the previous distance check made it difficult to load carried units into larger vehicles (e.g. trucks, aircraft).

moveInAny has a limitation for cargo seats: it places the unit into the seat with Position Number equal to the current number of cargo units, even if that seat is locked or already occupied.
This implementation includes a workaround: it uses temporary units and moveInCargo to shift the moveInAny position forward. However, it is not possible to shift it backwards. An approach based on pre-moveOut of units seems to be too buggy. As a result, in some cases loading into cargo may silently fail.

The main problem with cargo is reported in https://feedback.bistudio.com/T198758 and fixed in DEV 2.21.153732. Revision e373abf can run only on DEV. 3438b34 can still be used in 2.20.

Feedback is welcome, especially on naming and comments.