Indicate that DMAPI validation is taking place in world.params

[Absolucy]

Is your feature request related to a problem? Please describe.
DMAPI validation tends to have issues with things like byond-tracy, which can't detect that DMAPI validation is taking place (and it's a waste of time/memory/storage to use tracy it in the first place during validation), so having a flag set in world.params would be useful.

Describe the solution you'd like
A simple flag passed to DreamDaemon's world params indicating that DMAPI validation or such is taking place.

Describe alternatives you've considered
N/A

Additional context
N/A

[Cyberboss]

@Absolucy why not use PreCompile and PostCompile events to create a file that would only exist during DMAPI validation? Does that work?