Optimize ByteArray.iter a little bit

ByteArray.get performs a bounds check, which is redundant in
ByteArray.iter. Since it will likely take a while before the compiler is
able to remove bounds checking where possible, we'll need to do this by
hand in the mean time.

Changelog: performance

std/src/std/byte_array.inko

@@ -319,7 +319,11 @@ class builtin ByteArray {
     let max = size
 
     Stream.new fn move {
-      if idx < max { Option.Some(get(idx := idx + 1)) } else { Option.None }
+      if idx < max {
+        Option.Some(inko_byte_array_get(self, idx := idx + 1))
+      } else {
+        Option.None
+      }
     }
   }