Detect size of a vehicle and verify it can fit before spawning it

[3Mydlo3]

Currently there's a dumb implementation that uses 5 m radius check for obstacles at the spawn point. This might work well for cars, but it might be an issue for bigger helicopters (as their model center might be outside check radius, but blades will still be in range) or planes (which we don't have at the moment).

It should get replaced at some point, sizeOf was proposed during initial implementation in #63, but it's not ideal.

At least one object of the given classname has to be present in the current mission otherwise zero will be returned.
https://community.bistudio.com/wiki/sizeOf