RFR (S) 8244326: Shenandoah: global statistics should not accept bogus samples

[Roman Kennke]

>> Why not declare uninitialized a const field?
> 
> Wanted to maintain the symmetry against ShenandoahWorkerData::uninitialized(), which is
> WorkerDataArray<T>::uninitialized() in disguise:
> 
> template <>
> size_t WorkerDataArray<size_t>::uninitialized() {
>   return (size_t)-1;
> }
> 
> template <>
> double WorkerDataArray<double>::uninitialized() {
>   return -1.0;
> }

Hmm, ok then. The compiler will know what to do with it (I hope).

Roman