Make spritesheets cacheable by default, killing a lot of overtime in the round start spike (#80522)

## About The Pull Request
Makes all spritesheets cache by default. This wasn't the case originally
because some spritesheets like vending machines relied on in world
state, but none of them do anymore because that's whack.

Also fixes a bug that would cause half completed caches to break other
stuff. This didn't happen in real gameplay, but would've happened if you
tried to change cachable on anything while you already had a tmp folder.

## Changelog
🆑
fix: Cut down a significant amount of time that caused the start of
rounds to lag.
/🆑

code/modules/client/preferences/assets.dm

@@ -2,7 +2,6 @@
 /datum/asset/spritesheet/preferences
 	name = "preferences"
 	early = TRUE
-	cross_round_cachable = TRUE
 
 /datum/asset/spritesheet/preferences/create_spritesheets()
 	var/list/to_insert = list()

code/modules/client/preferences/middleware/antags.dm

@@ -108,7 +108,6 @@
 /datum/asset/spritesheet/antagonists
 	name = "antagonists"
 	early = TRUE
-	cross_round_cachable = TRUE
 
 	/// Mapping of spritesheet keys -> icons
 	var/list/antag_icons = list()

code/modules/client/preferences/middleware/species.dm

@@ -9,7 +9,6 @@
 /datum/asset/spritesheet/species
 	name = "species"
 	early = TRUE
-	cross_round_cachable = TRUE
 
 /datum/asset/spritesheet/species/create_spritesheets()
 	var/list/to_insert = list()