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/modules/mob/mob_defines.dm

@@ -5,6 +5,7 @@
 	movable_flags = MOVABLE_FLAG_PROXMOVE
 	sight = DEFAULT_SIGHT
 	blocks_emissive = EMISSIVE_BLOCK_GENERIC
+	pass_flags_self = PASSMOB
 	var/datum/mind/mind
 	var/static/next_mob_id = 0