Port SSoverlays & Convert turfs to use it (#5004)

* Added "Display Initialize() Log" admin debug command so you can see it mid-round.

* Ported the core of the overlays management subsystem from /tg

- Added SSoverlays subsystem for compiling overlay lists and applying them to atoms in a controlled anti-lag subsystem.
- Added vars and procs to atom which should eventually replace all direct interaction with BYOND's /atom/overlays var outside the subsystem.
- Added OVERLAY_QUEUED flag to var/atom/flags bitfield.
- Added small framework for subsystem performance tracking. So far used only by SSoverlays
- Added admin debug command "Display overlay Log" to see performance stats mid-round.

* Fix runtime on universal pipe adaptor update_icons

* Workaround for appearance_bro not initialized

Unfortuantely BYOND's initialization order is strange, and the appearance_bro var is only half initialized when map starts to load, causing errors.  We temporarily fix by moving it to be a global-scoped global.

* Convert fire alarms to use add_overlay() A good first test.

* Convert turfs to use add_overlays(), eliminating the turf_overlay_holder!

- Converted as much as I could find about turf overlays to use add_overlay().
- This should be enough to stop BYOND from crashing, so we can eliminate the turf_overlay_holder hack.
- This also lets us remove the anti-corruption hacks from walls and open space.
- ZAS gas overlays can use priority overlays, so this also fixes the gas-goes-away-when-crowbarring-plating issue.
- Stuff like that

* Convert turf overlay interactions to use add_overlay.

Note: This is a plain and simple conversion of existing code to use SSoverlays. However I look at the line changed, and note that that line likely never fully worked as intended, as it has no way of re-applying itself.
I would make it use a priority overlay, but there is no code present for *removing* said overlay from neighbors when it is no longer required.  That code should be implemented by original author.

code/modules/admin/admin_verbs.dm

@@ -193,6 +193,8 @@ var/list/admin_verbs_debug = list(
 	/client/proc/cmd_debug_del_all,
 	/client/proc/cmd_debug_tog_aliens,
 	/client/proc/cmd_display_del_log,
+	/client/proc/cmd_display_init_log,
+	/client/proc/cmd_display_overlay_log,
 	/client/proc/air_report,
 	/client/proc/reload_admins,
 	/client/proc/reload_eventMs,