Mecha spark system runtime on destruction. Fixes mecha draining infinite powercells

[ShizCalev]

:cl: ShizCalev fix: Fixed mechas with infinite powercells draining the cells on destruction /:cl:

take_damage()'s parent chain starts the atom's qdel, so spark_system was null by the time it was called. This stopped the final hit from being logged properly.

Also cleaned up a duplicate definition for mecha/atom_destruction