Works around a problem in the old Lua API where a trait lookup would
not find the correct class and make the script crash.
In this instance, `Game.modData.ObjectCreator.FindType("RallyPoint")`
return `OpenRA.Mods.Common.Effects.RallyPoint` instead of the expected
`OpenRA.Mods.Common.RallyPoint`.
The other change is an oversight from the recent warhead rewrites.
Fixes#6728
Changes included:
Warhead code split out of weapon code and refactored.
Warhead functionality now split into several classes, each handling one effect/impact.
Additional custom warheads can now be defined and called via yaml.
Custom warheads inherit the abstract class Warhead,
which provides target check functions.
Custom warheads have to define their own impact functions,
and can also define their own replacement for check
functions.
