swift

80f38495 - [Concurrency] Parent task cancellation must cancel task group itself.

[Concurrency] Parent task cancellation must cancel task group itself. Seems that during refactorings of child cancellations we somehow missed also cancelling the group itself. It seems we did not have good test coverage of the addTaskUnlessCancelled somehow and thus this slipped through. This adds a regression test for addTaskUnlessCancelled and fixes how we handle the cancellation effect in TaskStatus. resolves #80789 resolves rdar://149177600