Added CopyToAsync overload using default buffer size (#14219)
Added CopyToAsync overload using default buffer size (#14219)

* Added CopyToAsync overload using default buffer size

* Address feedback

* Added comment about overrides and argument validation

* Renamed helper method to GetCopyBufferSize

To convey that this method should only be used for
getting a buffer size to be passed to CopyTo{Async}.

JosephTremoulet/coreclr,yizhang82/coreclr,wateret/coreclr,hseok-oh/coreclr,parjong/coreclr,poizan42/coreclr,wtgodbe/coreclr,botaberg/coreclr,poizan42/coreclr,poizan42/coreclr,rartemev/coreclr,yizhang82/coreclr,krk/coreclr,rartemev/coreclr,mmitche/coreclr,botaberg/coreclr,krk/coreclr,botaberg/coreclr,poizan42/coreclr,krk/coreclr,wateret/coreclr,wateret/coreclr,botaberg/coreclr,parjong/coreclr,yizhang82/coreclr,kyulee1/coreclr,cshung/coreclr,wtgodbe/coreclr,kyulee1/coreclr,parjong/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,cshung/coreclr,parjong/coreclr,mmitche/coreclr,yizhang82/coreclr,wtgodbe/coreclr,hseok-oh/coreclr,kyulee1/coreclr,krk/coreclr,wtgodbe/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,kyulee1/coreclr,JosephTremoulet/coreclr,botaberg/coreclr,rartemev/coreclr,poizan42/coreclr,cshung/coreclr,poizan42/coreclr,yizhang82/coreclr,rartemev/coreclr,mmitche/coreclr,cshung/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,kyulee1/coreclr,ruben-ayrapetyan/coreclr,hseok-oh/coreclr,parjong/coreclr,rartemev/coreclr,mmitche/coreclr,kyulee1/coreclr,cshung/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,rartemev/coreclr,cshung/coreclr,ruben-ayrapetyan/coreclr,botaberg/coreclr,JosephTremoulet/coreclr,wateret/coreclr,mmitche/coreclr,parjong/coreclr,wateret/coreclr,mmitche/coreclr,JosephTremoulet/coreclr,wtgodbe/coreclr,hseok-oh/coreclr,wateret/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr