Two for one bonus special!

Fixes #6524

There are two issues at play here:

• An entity is trying to unjam an RAC on the same turn that its fled the map. Once an entity flees, it is null, so the unjam step cannot be properly processed.
  • This is handled by adding a null entity check in resolveUnjam.
  • I suspect a similar bug will occur for other cases in TWGameManager::resolveAllButWeaponAttacks. I considered putting the null entity check there, but several of these actions still need to be processed even if the entity has fled, like clearing a minefield or activating an AP pod. I think we should handle these cases as they occur.
  • This only became an issue when we enabled fleeing at the end of movement. Prior to that a unit would never be null before processing its unjam step.
• Tanks were able to unjam "weapon malfunction" crits (TW p. 195) in the movement phases using the "Unjam RAC" which is meant to be used for the RAC or other rapid fire weapons if the setting is enabled.
  • Tank weapons that are jammed because of that are added to a special list that only tanks have. When checking if a weapon can be unjammed in the manner of rapid-fire weapons we first check if the weapon was jammed from a weapon malfunction crit - if it was we can't unjam it using this action.