Makes energy gun cells bomb proof. Makes the cells of indestructible energy guns also indestructible. (#91284)

## About The Pull Request

The cell contained within energy guns can sometimes be destroyed due
to...reasons. This makes it so that the cell is bombproof, and if the
gun is indestructible, also indestructible for good measure.

## Why It's Good For The Game

This is basically a constant problem that doesn't seem to ever go away
due to the fact that the cell is an actual physical object and not an
abstraction.

While it remains an actual object, lets just...make it not break and
brick an important item, yeah?

## Changelog
🆑
fix: If an energy weapon is indestructible, so is the cell within the
weapon.
fix: Cells inside of energy guns are bomb proof so as to not brick a gun
that somehow survives being bombed.
/🆑

code/__DEFINES/_flags.dm

@@ -222,6 +222,8 @@ GLOBAL_LIST_INIT(bitflags, list(1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 204
 #define FREEZE_PROOF (1<<7)
 /// can't be shuttle crushed.
 #define SHUTTLE_CRUSH_PROOF (1<<8)
+/// can't be destroyed by bombs
+#define BOMB_PROOF (1<<9)
 
 //tesla_zap
 #define ZAP_MACHINE_EXPLOSIVE (1<<0)

code/_globalvars/bitfields.dm

@@ -352,7 +352,8 @@ DEFINE_BITFIELD(resistance_flags, list(
 	"ACID_PROOF" = ACID_PROOF,
 	"INDESTRUCTIBLE" = INDESTRUCTIBLE,
 	"FREEZE_PROOF" = FREEZE_PROOF,
-	"SHUTTLE_CRUSH_PROOF" = SHUTTLE_CRUSH_PROOF
+	"SHUTTLE_CRUSH_PROOF" = SHUTTLE_CRUSH_PROOF,
+	"BOMB_PROOF" = BOMB_PROOF,
 ))
 
 DEFINE_BITFIELD(sight, list(

code/game/objects/obj_defense.dm

@@ -8,7 +8,7 @@
 	take_damage(damage_taken, BRUTE, MELEE, 1, get_dir(src, hit_by))
 
 /obj/ex_act(severity, target)
-	if(resistance_flags & INDESTRUCTIBLE)
+	if(resistance_flags & (INDESTRUCTIBLE|BOMB_PROOF))
 		return FALSE
 
 	. = ..() //contents explosion

code/modules/projectiles/guns/energy.dm

@@ -93,6 +93,9 @@
 		cell = new(src)
 	if(!dead_cell)
 		cell.give(cell.maxcharge)
+	if(cell && resistance_flags & INDESTRUCTIBLE)
+		cell.resistance_flags |= INDESTRUCTIBLE
+	cell.resistance_flags |= BOMB_PROOF
 	update_ammo_types()
 	recharge_newshot(TRUE)
 	if(selfcharge)