Enhances algorithm for finding an atom mount (#94076)

## About The Pull Request
Depends on #94064 for the unit test but offers a better method for
finding an atom to mount on
- Finding a mount now takes into consideration the objects pixel x & y
offsets meaning diagonal mounting is now supported. Gives great
flexibility for mappers
- If you don't want to use pixel offsets but default back to using the
objects direction that behaviour is still preserved. Useful if your
object uses directional icon states(lights & cameras for now) AND don't
use offsets
- If no direction could be specified then as the last resort it defaults
back to the objects local turf for mounting

## Changelog
🆑
fix: all mounted objects on tables, fences, windows & walls should fall
of correctly when the atom it is placed on is destroyed
fix: security telescreen now falls off when their mounted wall is
destroyed
fix: defib wall mount falls off when their mounted wall is destroyed
fix: floor lights are mounted to the ground/catwalk/tram floor they are
sitting on meaning destroying it will destroy the light
fix: wall mounted plaques now fall off when their mounted wall is
destroyed
/🆑

code/modules/security_levels/keycard_authentication.dm

@@ -26,6 +26,8 @@ GLOBAL_DATUM_INIT(keycard_events, /datum/events, new)
 /obj/machinery/keycard_auth/Initialize(mapload)
 	. = ..()
 	activated = GLOB.keycard_events.addEvent("triggerEvent", CALLBACK(src, PROC_REF(triggerEvent)))
+	if(mapload)
+		find_and_mount_on_atom()
 
 /obj/machinery/keycard_auth/Destroy()
 	GLOB.keycard_events.clearEvent("triggerEvent", activated)
@@ -162,11 +164,6 @@ GLOBAL_DATUM_INIT(keycard_events, /datum/events, new)
 
 MAPPING_DIRECTIONAL_HELPERS(/obj/machinery/keycard_auth/wall_mounted, 26)
 
-/obj/machinery/keycard_auth/wall_mounted/Initialize(mapload)
-	. = ..()
-	if(mapload)
-		find_and_hang_on_atom()
-
 GLOBAL_VAR_INIT(emergency_access, FALSE)
 /proc/make_maint_all_access()
 	for(var/area/station/maintenance/area in GLOB.areas)