[DNM][DNM][WIP] Projectile backend code port and update

Ports#54924,  #65061, #59804 from /tg.
adds auxiliary code from /tg to make code work.

code/modules/projectiles/projectile/bullets/sniper.dm

@@ -35,7 +35,8 @@
 	icon_state = "gauss"
 	name = "penetrator round"
 	damage = 60
-	movement_type = FLYING | UNSTOPPABLE
+	projectile_piercing = PASSMOB
+	projectile_phasing = (ALL & (~PASSMOB))
 	dismemberment = 0 //It goes through you cleanly.
 	knockdown = 0
 	breakthings = FALSE