Exceptiongroup

- Updated the copying of ``__notes__`` to match CPython behavior (PR by CF Bolz-Tereick)
- Corrected the type annotation of the exception handler callback to accept a
``BaseExceptionGroup`` instead of ``BaseException``
- Fixed type errors on Python < 3.10 and the type annotation of ``suppress()``
(PR by John Litborn)

- Added special monkeypatching if `Apport <https://github.com/canonical/apport>`_ has
overridden ``sys.excepthook`` so it will format exception groups correctly
(PR by John Litborn)
- Added a backport of ``contextlib.suppress()`` from Python 3.12.1 which also handles
suppressing exceptions inside exception groups
- Fixed bare ``raise`` in a handler reraising the original naked exception rather than
an exception group which is what is raised when you do a ``raise`` in an ``except*``
handler

- ``catch()`` now raises a ``TypeError`` if passed an async exception handler instead of
just giving a ``RuntimeWarning`` about the coroutine never being awaited. (66, PR by
John Litborn)
- Fixed plain ``raise`` statement in an exception handler callback to work like a
``raise`` in an ``except*`` block
- Fixed new exception group not being chained to the original exception when raising an
exception group from exceptions raised in handler callbacks
- Fixed type annotations of the ``derive()``, ``subgroup()`` and ``split()`` methods to
match the ones in typeshed

- Changed handling of exceptions in exception group handler callbacks to not wrap a
single exception in an exception group, as per
`CPython issue 103590 <https://github.com/python/cpython/issues/103590>`_

- Worked around
`CPython issue 98778 <https://github.com/python/cpython/issues/98778>`_,
``urllib.error.HTTPError(..., fp=None)`` raises ``KeyError`` on unknown attribute
access, on affected Python versions. (PR by Zac Hatfield-Dodds)

- Backported upstream fix for gh-99553 (custom subclasses of ``BaseExceptionGroup`` that
also inherit from ``Exception`` should not be able to wrap base exceptions)
- Moved all initialization code to ``__new__()`` (thus matching Python 3.11 behavior)