Removes bad nodamage var from projectiles, fixes Juggernaut / Rust Walker projectiles doing zero damage (#73806)

## About The Pull Request

- Juggernaut and Rust Walker projectiles were subtyped off of magic,
which is `nodamage`.

- The juggernaut actually had a copy+paste error with their type
`on_hit` which caused none of their special effects on hit ("relative
patching catches this")

- Then I realized projectiles have this var `nodamage` which is, for all
intents and purposes, just `damage > 0`. it's not checked for pacifism,
it's just that. This is dumb. So very dumb, so I removed it.
- There are, however, a few situations which used it in a unique way,
such as the blast wave cannon. This is why I replaced it with a proc,
`is_hostile_projectile`, for certain situations to actually find out if
the projectile is damaging. Projectiles can override this on a per type
basis by default, damaging projectiles = hostile.
- This has a chance to break some things, but I ... kinda doubt it will.

Fixes #73756

## Why It's Good For The Game

Projectiles that act as they should, less dumb vars

## Changelog

🆑 Melbert
fix: Fixes Juggernaut / Rust Walker projectiles doing zero damage
fix: Fixes Juggernaut projectiles not doing bonus damage to nearby
structures
code: Removed projectile nodamage var, replaces it with just checking
for damage
/🆑

code/modules/power/rtg.dm

@@ -76,7 +76,7 @@
 
 /obj/machinery/power/rtg/abductor/bullet_act(obj/projectile/Proj)
 	. = ..()
-	if(!going_kaboom && istype(Proj) && !Proj.nodamage && ((Proj.damage_type == BURN) || (Proj.damage_type == BRUTE)))
+	if(!going_kaboom && istype(Proj) && Proj.damage > 0 && ((Proj.damage_type == BURN) || (Proj.damage_type == BRUTE)))
 		log_bomber(Proj.firer, "triggered a", src, "explosion via projectile")
 		overload()