[#1933] Validate impulse_request values

[oznogon]

#1933 shows that directly setting impulse_request on a SpaceShip can result in unusable or poorly defined values, such as infinity/-infinity from dividing by 0 impulse speed on Odins and Defense Platforms.

Add a setImpulseRequest() function that clamps the passed value and replace direct modifications of impulse_request with it.

Fixes #1933.

[daid]

I see I totally forgot to reply to this.

While the idea is feels sound on the first glance. There is an issue with it. It's still dividing by zero, and assuming that it will produce "infinity". But as we are compiling with -funsafe-math-optimizations this does not have to be true, and division by zero is can be UB or an exception, so we should avoid it in the first place.

[oznogon]

Added a check to confirm that impulse_max_speed is greater than 0 before attempting setImpulseRequest.