Small hulk cleanup / nukes TRAIT_IGNOREDAMAGESLOWDOWN (#85003)

## About The Pull Request

I was investigating a bug with hulk in which using it while damaged
doesn't put you back on full speed

I noticed `TRAIT_IGNOREDAMAGESLOWDOWN` on its own was subtly broken, in
that it did nothing if the user did not call `updatehealth` afterwards

And guess what, most (if not all) uses of the trait did not do this, so
it never applied correctly

So I nuked the trait entirely, made all uses of it use the same thing
morphine uses (`/datum/movespeed_modifier/damage_slowdown`)

And since I was auditing this I saw the ball module was broke, it
removed the immunity but never added it. Quick fix

I also cleaned up some Hulk stuff while I was in the area because I was
in the area. I removed all instances of `check_mutation` and replaced it
with trait checking because it made more sense.

I also also fixed a bug with the simple flying element never removing on
detach because I touched something that uses it for the above change.

## Changelog

🆑 Melbert
fix: Using hulk (and a myriad of similar effects) now properly updates
your movespeed to ignore the damage movespeed penalty
fix: Some things which temporarily make you fly don't make you fly
forever
fix: MODsuit ball module now properly makes you immune to damage
movespeed penalty when in ball form
fix: Adding Hulk via VV dropdown doesn't default to adding the strongest
hulk available (that which is used by the medieval pirates)
/🆑

code/modules/mod/modules/modules_supply.dm

@@ -499,6 +499,7 @@
 	mod.wearer.add_traits(user_traits, MOD_TRAIT)
 	mod.wearer.RemoveElement(/datum/element/footstep, FOOTSTEP_MOB_HUMAN, 1, -6)
 	mod.wearer.AddElement(/datum/element/footstep, FOOTSTEP_OBJ_ROBOT, 1, -6, sound_vary = TRUE)
+	mod.wearer.add_movespeed_mod_immunities(MOD_TRAIT, /datum/movespeed_modifier/damage_slowdown)
 	mod.wearer.add_movespeed_modifier(/datum/movespeed_modifier/sphere)
 	RegisterSignal(mod.wearer, COMSIG_MOB_STATCHANGE, PROC_REF(on_statchange))