PEP-654 ExceptionGroup support in python<3.11

[John Litborn]

Hello,
python3.11 introduced ExceptionGroups[1], which Apport manages to format perfectly fine on python>=3.11 - but there is a backport package[2] for python<3.11 which relies on monkeypatching sys.excepthook to reformat the exception and get it to properly print sub-exceptions. This clashes with Apport, which also monkeypatches sys.excepthook in order to collect debugging information.
I recently wrote a PR[3] to the exceptiongroup repo with a messy workaround to work with Apport, but it would be much cleaner if Apport could make use of the backport package itself - and that would also avoid issues that might arise from Apport changing its hook[4]

[1] PEP 654: https://peps.python.org/pep-0654/
[2] Backport package: https://github.com/agronholm/exceptiongroup
[3] ExceptionGroup PR: https://github.com/agronholm/exceptiongroup/pull/88
[4] Issue that arose when apport renamed its hook https://github.com/python-trio/trio/issues/2464

Issue in agronholm/exceptiongroup that discusses adaption of the backport in various packages: https://github.com/agronholm/exceptiongroup/issues/23

I might be able to write a PR that implements it and submit it to your GitHub in case you deem this valuable but low priority.