Add TaskCompletionSource.SetCanceled(CancellationToken) (#32696)

Add TaskCompletionSource.SetCanceled(CancellationToken) (#32696)

* Add TaskCompletionSource.SetCanceled(CancellationToken)

api-approved by #30862

* Add to ref

* SetCanceled(default)

* Change some tests to use SetCaneled not TrySetCanceled

These tests used SetResult/SetException and TrySetCancelled so it could
pass a token. Changed to use SetCancelled to match the Result/Exception
useage.

* Add SetCanceled(CT) test

* Check exception on re-cancel

* Equal not Equals

* Catch aggregate not TaskCancelled directly

*  Inner not exc

* Markup

* s/m/n