VarAction2: Re-order commutative skip on zero operation sequences

Such that less expensive variables can be tested first

src/debug_settings.h

@@ -33,6 +33,7 @@ enum NewGRFOptimiserFlags {
 	NGOF_NO_OPT_VARACT2_GROUP_PRUNE     = 2,
 	NGOF_NO_OPT_VARACT2_EXPENSIVE_VARS  = 3,
 	NGOF_NO_OPT_VARACT2_SIMPLIFY_STORES = 4,
+	NGOF_NO_OPT_VARACT2_ADJUST_ORDERING = 5,
 };
 
 inline bool HasGrfOptimiserFlag(NewGRFOptimiserFlags flag)