Provide doc comments for AsyncSequence and related types (#37383)
* First draft docs for iterator, sequence type.
Also drop(while:), to get a feel for the AsyncSequence->AsyncSequence cases.
* Source docs for contains and reduce.
* Docs for methods in AsyncSequence.
This covers all the methods that return a single value. Still working on the extension methods that return new sequences.
* Early source docs for dropFirst(_:) and its type
* Correct doc format for dropFirst(_:).
* Prefix, plus some fixes.
* Docs for prefix(while:).
* Apply Philippe's snippet fixes.
* First draft docs on the map sequences.
Plus miscellaneous fixes throughout.
* Show result of flatMap example.
* More explicit cancellation guidance.
* Convert snippets to trailing closures.
* Correct misplaced doc comments.
* Apply suggestions from code review
Co-authored-by: Philippe Hausler <phausler@apple.com>
* Apply editorial feedback.
* Apply additional editorial feedback.
* Apply suggestions from code review
Co-authored-by: bjlanier <blanier@apple.com>
* Apply further editorial feedback.
Co-authored-by: Chris Adamson <cadamson@apple.com>
Co-authored-by: Philippe Hausler <phausler@apple.com>
Co-authored-by: bjlanier <blanier@apple.com>
