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.dm

@@ -3,6 +3,7 @@
 	w_class = WEIGHT_CLASS_GIGANTIC
 	layer = STRUCTURE_LAYER
 	blocks_emissive = EMISSIVE_BLOCK_GENERIC
+	pass_flags_self = PASSSTRUCTURE
 
 	var/material_alteration = MATERIAL_ALTERATION_ALL // Overrides for material shit. Set them manually if you don't want colors etc. See wood chairs/office chairs.
 	var/climbable