asDiscrete: the levels parameter works inconsistently with values of int type

In the legend, I expect the order `3, 2, 1` (reversed, `order=-1`) for `levels=1, 2, 3`. The actual order is `2, 1, 3`, which looks like the reversed data order, i.e., the levels parameter is ignored:

```kotlin
%useLatestDescriptors
%use lets-plot

val d = mapOf(
"x" to listOf(0, 1, 2),
"v" to listOf(3, 1, 2),
)

ggplot(d) + geomPoint {
x = "x";
color = asDiscrete("v", levels=listOf(1, 2, 3), order=-1)
}
```


Without `order=-1`, the int levels are handled properly:

With doubles, the `levels` parameters handled properly even with the `order` parameter:

Version:
```
Lets-Plot Kotlin API v.4.7.3. Frontend: Notebook with dynamically loaded JS. Lets-Plot JS v.4.3.3.
```