[3.14] gh-101267: ProcessPoolExecutor no longer shares 1 BrokenProcessPool exception...

[3.14] gh-101267: ProcessPoolExecutor no longer shares 1 BrokenProcessPool exception among all failed futures (GH-101268) (#151431)

* gh-101267: ProcessPoolExecutor no longer shares 1 BrokenProcessPool exception among all failed futures (GH-101268)
(cherry picked from commit 3c00ebc2bbd902495b163def850bc931420209fc)

Co-authored-by: Daniel Shields <daniel.shields@twosigma.com>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
(cherry picked from commit 4e8c9c6a5742659ca9f77719178802cce06a3507)

* Drop the abrupt-exit-code reporting from the 3.14 backport

Reporting the exit codes of processes that died without a known cause
is a new feature, not part of the gh-101267 bugfix. Keep only the
bugfix on 3.14: each failed future gets its own BrokenProcessPool
exception instead of one shared instance.

---------

Co-authored-by: Daniel Shields <daniel.shields@twosigma.com>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>