Port VOREStation PR 6914 Speed up map load significantly

- Set initialized = FALSE on unsimulated turfs that need to intialize.
- Most of area/New() to initialize
- Faster lookup of self-init on atoms
- Split air alarm and fire alarm files, move new to initialize
- Tweak decals and opacity

Co-authored-by: Aronai Sieyes <arokha@arokha.com>
Co-authored-by: Leshana <Leshana@users.noreply.github.com>

code/modules/overmap/_defines.dm

@@ -33,8 +33,8 @@ var/global/list/map_sectors = list()
 	opacity = 1
 	density = 1
 
-/turf/unsimulated/map/New()
-	..()
+/turf/unsimulated/map/Initialize()
+	. = ..()
 	name = "[x]-[y]"
 	var/list/numbers = list()