`Spring.GetCEGID("nonexistent ceg")` allocates a new ID

[sprunk]

• it never returns invalid for nonexistent CEG names, instead it allocates a new ID for them and then returns that ID consistently for given name. So there is no way to check if given CEG actually exists or not.
• not a realistic scenario but by allocating variable numbers of garbage CEGs you can get a desync if synced luarules ever asks about a nonexistent ceg and uses the returned ID.

[sprunk]

It should be a matter of splitting the "find generator" part away from CExplosionGeneratorHandler::LoadGenerator and using that in Spring.GetCEGID instead of the full function that allocates a new one if missing: https://github.com/beyond-all-reason/spring/blob/7363dbc54b55d309539b92c60245f88afd1f4e4a/rts/Sim/Projectiles/ExplosionGenerator.cpp#L296-L309