OpHelpers returning non-int values lead to Infinite bailouts on some array operations

```
var index = "0.1";
var ary = [0,1];

for (var i = 0; i < 10000; ++i)
{
// +index calls Op_ConvNumber which will return a double in this case.
// LdElemI will does a type check on the index and bails out if it's not an int, but rejits the exact same code.
ary[+index];
}
```