Converting meteors into projectiles

Created by: dylanstrategie

Redux of #8281

• Meteors are now projectiles and use projectile code to move around instead of walk_towards. This should make good use of the projectile move procs and allow us to target meteors and still have them keep moving, which will be useful later on
• Change probability weight. 100 is normal meteor weight, small meteors are 80, large meteors are 10. All special meteor types are ten times less likely than their parent
• Meteors that cross over a mob (same code as syndicate wheelchair and hacked MULEbot) will now fire Bump(), aka explosion. This prevents players from cheesing meteor waves by simply laying down in space, now they have to actually dodge the rocks
• A bunch of path updates, and old meteor projectile that was used for that weird meteor launcher bus weapon has been removed. I haven't tested that weapon, but it might just werk
• Attempt to fix cluster meteors, for some reason they sometimes don't get a destination
• Meteors are no longer deleted when hitting transition zones but still can't cross into other Z-levels

New changes :

• Projectiles now have INFINITY as a kill_count. This means that most projectiles won't delete themselves fifty tiles in for no reason. And indeed, there's no reason, from optimization to gameplay, to have this for things like bullets or rockets

Tested, no runtimes