The following fixes are made:
- cancelling a gather now cancels all sub-tasks of the gather (previously
it would only cancel the first)
- if any sub-task of a gather raises an exception then the gather finishes
(previously it would only finish if the first sub-task raised)
Fixes issues #5798, #7807, #7901.
Signed-off-by: Damien George <damien@micropython.org>
Damien George