[C++] Create enumerating generator #28093
Description
With parallel readahead items may get returned out of order. An enumerating future can be used to tag items prior to the parallel readahead so that they can later be reassembled.
Reporter: Weston Pace / @westonpace
Assignee: Weston Pace / @westonpace
PRs and other links:
Note: This issue was originally created as ARROW-12287. Please see the migration documentation for further details.