Demotes the "electrical conductivity" flag from flags_1 to obj_flags (#80033)

## About The Pull Request

Code to handle this flag only ever existed on the `/obj` sublevel, so
there's no need for it to be on the `/atom` level `flags_1`. There was
probably a point in time in which mobs or turfs conducted electricity
but there's zero code for it anymore so we truly just live in a society
now.
## Why It's Good For The Game

Frees up a slot on `flags_1` (which is really nice actually), proper
scoping of certain bitflag stuff, etc.
## Changelog
Not relevant to players.

I may have screwed something up, will be doing a few passes on this
myself to ensure all the search and replaces went alright but we should
be good™️

code/modules/assembly/assembly.dm

@@ -4,7 +4,7 @@
 	desc = "A small electronic device that should never exist."
 	icon = 'icons/obj/assemblies/new_assemblies.dmi'
 	icon_state = ""
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	w_class = WEIGHT_CLASS_SMALL
 	custom_materials = list(/datum/material/iron=SMALL_MATERIAL_AMOUNT)
 	throwforce = 2

code/modules/assembly/bomb.dm

@@ -8,7 +8,7 @@
 	w_class = WEIGHT_CLASS_NORMAL
 	throw_speed = 2
 	throw_range = 4
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	var/status = FALSE   //0 - not readied //1 - bomb finished with welder
 	var/obj/item/assembly_holder/bombassembly = null   //The first part of the bomb is an assembly holder, holding an igniter+some device
 	var/obj/item/tank/bombtank = null //the second part of the bomb is a plasma tank

code/modules/assembly/holder.dm

@@ -5,7 +5,7 @@
 	inhand_icon_state = "assembly"
 	lefthand_file = 'icons/mob/inhands/items/devices_lefthand.dmi'
 	righthand_file = 'icons/mob/inhands/items/devices_righthand.dmi'
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	throwforce = 5
 	w_class = WEIGHT_CLASS_SMALL
 	throw_speed = 2

code/modules/assembly/shock_kit.dm

@@ -6,7 +6,7 @@
 	var/obj/item/clothing/head/helmet/helmet_part = null
 	var/obj/item/electropack/electropack_part = null
 	w_class = WEIGHT_CLASS_HUGE
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 
 /obj/item/assembly/shock_kit/Destroy()
 	QDEL_NULL(helmet_part)