[3.15] gh-101267: ProcessPoolExecutor no longer shares 1 BrokenProcessPool exception among all failed futures (GH-101268) (#151430)

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>
4 files changed