Mob Ref Cleanup Part 3 (#22599)

Part 3 of the Mob Destroy Refactor, this time going through the entire
list of every ref stored up to a mob/human, and (attempting) to verify
and cleanup every possible circular ref. This PR also fixes some
mistakes made with cleaning up UI elements, namely that tgui's really
don't like it when you qdel them, and screen objects also weren't always
clearing their own references if Qdel'ed directly. There were several
niche situations too where circle refs might be retained by a mob. I
also found an issue where static lights were only cleaned up on
/atom/movable/ but actually existed farther up the chain on /atom. I
don't know if any /atoms that aren't /atom/movable ever get static
lights, but the fact that they can be needs to be correctly accounted
for.

I can't possibly have gotten all of them, but this is every single one I
could find after 3 hours of work.

code/modules/mob/mob.dm

@@ -54,6 +54,8 @@
 
 	QDEL_NULL(ability_master)
 	QDEL_NULL(zone_sel)
+	if (length(machine?.climbers))
+		machine.climbers -= src
 	machine = null
 
 	client_colors = null
@@ -61,6 +63,7 @@
 	pinned?.Cut()
 	QDEL_LIST(embedded)
 	languages?.Cut()
+	holo?.clear_holo(src)
 	holo = null
 	l_hand = null
 	r_hand = null
@@ -104,11 +107,23 @@
 	QDEL_LIST(click_handlers)
 	vr_mob = null
 	old_mob = null
+	if (lastattacker && lastattacker.lastattacked == src)
+		lastattacker.lastattacked = null
+	if (lastattacked && lastattacked.lastattacker == src)
+		lastattacked.lastattacker = null
 	lastattacker = null
 	lastattacked = null
 	QDEL_NULL(pointing_effect)
-	QDEL_LIST(open_nanouis)
-	QDEL_LIST(tgui_open_uis)
+
+	// Cleanup for all UIs belonging to the client.
+	// For performance reasons we check the length of the lists first since the lists can potentially either be null or empty.
+	// But it's also plausible that they might contain null values, and while their aggressive checking means any valid entry in the list
+	// is guaranteed to be of type /datum/tgui, null entries in the list can potentially exist and will pass the as anything typecast.
+	if (length(tgui_open_uis))
+		for (var/datum/tgui/ui as anything in tgui_open_uis)
+			ui?.close()
+		tgui_open_uis.Cut()
+
 	QDEL_NULL(narsimage)
 	QDEL_NULL(narglow)
 	QDEL_NULL(riftimage)