[regression][js] Std.is(_, Int) often not optimized

In haxe 4 these all used to be optimized, while in haxe 5 it [only seems to work for `Dynamic`](https://try.haxe.org/#38C167cD):

```haxe
function main() {
var v:Dynamic = 0;
trace(Std.is(v, Int)); // typeof(v) == "number" && ((v | 0) === v)
var v:Any = v;
trace(Std.is(v, Int)); // js_Boot.__instanceof(v1,Int)
var v:Int = v;
trace(Std.is(v, Int)); // js_Boot.__instanceof(v1,Int)
}
```

Also checking against `Float` seems to always work.