Moves space initialization check to unit test - Saves 0.065s of init time (#71796)

This hasn't been hit in a long time and this is an extremely hot proc,
doing these checks in unit tests should catch any cases, though
unlikely.

This has zero cost at runtime because `if (FALSE)` statically compiles
out.

code/game/turfs/open/space/space.dm

@@ -47,8 +47,9 @@
 	SHOULD_CALL_PARENT(FALSE)
 	air = space_gas
 
-	if(flags_1 & INITIALIZED_1)
-		stack_trace("Warning: [src]([type]) initialized multiple times!")
+	if (PERFORM_ALL_TESTS(focus_only/multiple_space_initialization))
+		if(flags_1 & INITIALIZED_1)
+			stack_trace("Warning: [src]([type]) initialized multiple times!")
 	flags_1 |= INITIALIZED_1
 
 

code/modules/unit_tests/focus_only_tests.dm

@@ -15,5 +15,8 @@
 /// Checks that every icon sent to vending machines is valid
 /datum/unit_test/focus_only/invalid_vending_machine_icon_states
 
+/// Checks that space does not initialize multiple times
+/datum/unit_test/focus_only/multiple_space_initialization
+
 /// Checks that smoothing_groups and canSmoothWith are properly sorted in /atom/Initialize
 /datum/unit_test/focus_only/sorted_smoothing_groups