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/game/objects/structures/cannons/cannonballs.dm

@@ -7,7 +7,7 @@
 	singular_name = "cannonball"
 	merge_type = /obj/item/stack/cannonball
 	throwforce = 10
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	custom_materials = list(/datum/material/alloy/plasteel=SHEET_MATERIAL_AMOUNT)
 	resistance_flags = FIRE_PROOF
 	throw_speed = 5

code/game/objects/structures/grille.dm

@@ -10,7 +10,7 @@
 	density = TRUE
 	anchored = TRUE
 	pass_flags_self = PASSGRILLE
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	obj_flags = CAN_BE_HIT | IGNORE_DENSITY
 	pressure_resistance = 5*ONE_ATMOSPHERE
 	armor_type = /datum/armor/structure_grille
@@ -280,7 +280,7 @@
 			return
 //window placing end
 
-	else if((W.flags_1 & CONDUCT_1) && shock(user, 70))
+	else if((W.obj_flags & CONDUCTS_ELECTRICITY) && shock(user, 70))
 		return
 
 	return ..()

code/game/objects/structures/tables_racks.dm

@@ -902,7 +902,7 @@
 	icon = 'icons/obj/structures.dmi'
 	icon_state = "rack_parts"
 	inhand_icon_state = "rack_parts"
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	custom_materials = list(/datum/material/iron=SHEET_MATERIAL_AMOUNT)
 	var/building = FALSE
 

code/game/objects/structures/training_machine.dm

@@ -350,7 +350,7 @@
 	inhand_icon_state = "toolbox_gold"
 	lefthand_file = 'icons/mob/inhands/equipment/toolbox_lefthand.dmi'
 	righthand_file = 'icons/mob/inhands/equipment/toolbox_righthand.dmi'
-	flags_1 = CONDUCT_1
+	obj_flags = CONDUCTS_ELECTRICITY
 	force = 0
 	throwforce = 0
 	throw_speed = 2