Reformat and increase minimum arena capacity to 4 pages

tests/arena/test_arena.c

@@ -6,7 +6,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#define ARENA_CAPACITY 1024
+#define ARENA_CAPACITY KB(16)
 
 internal Arena *arena = NULL;
 internal i32 count    = 20;