Flags and adjacency work (#20259)

Added a bunch of flags for passflags on things that were previously
missing them.
Removed snowflake passthrow var, it's a passflag now.
Updated ClickCross and Adjacency code.
It's now possible to interact with things that are adjacent but
otherwise have a machine (or other appropriate items) blocking them, eg.
think of an APC on the wall with a machine in front of it.

code/game/objects/structures/railing.dm

@@ -4,7 +4,6 @@
 	icon = 'icons/obj/structure/blocker/railing_basic.dmi'
 	icon_state = "railing0-1"
 	density = TRUE
-	throwpass = TRUE
 	climbable = TRUE
 	layer = OBJ_LAYER
 	anchored = FALSE