Refactors body markings into bodypart overlays (#83744)

## About The Pull Request
Refactors body markings (lizard and moths) into the bodypart overlays
system
I've also renamed the icon states for lizard bodymarkings (downstreams
with lots of lizard body markings might have problems with this)

## Why It's Good For The Game
Gives us better controle over /human appearances. I didn't add any means
of actually changing them on the person (aside from genetics. how would
that even work? with a waterproof marker?), but makes it easy for
when/if I do. Also unloads mutant_bodyparts more, moving is yet closer
to full species dedatumization

## Changelog
🆑
refactor: Lizard and moth markings now use the bodypart overlay system
/🆑

code/modules/mining/lavaland/megafauna_loot.dm

@@ -755,7 +755,7 @@
 				"wings" = "None",
 				"frills" = "None",
 				"spines" = "Long",
-				"body_markings" = "Dark Tiger Body",
+				"lizard_markings" = "Dark Tiger Body",
 				"legs" = DIGITIGRADE_LEGS,
 			)
 			consumer.eye_color_left = "#FEE5A3"