some usages of sys.exc_info can be replaced by more modern code

[iritkatriel]

There are some obvious places where sys.exc_info() can be replaced by direct access to a captured exception (without needing any new features that could complicate backports.)

Need to avoid changing tests that are testing exc_info, like generator tests or sys.

Linked PRs

• gh-102799: remove unnecessary calls to sys.exc_info() in tests #102800
• gh-102799: Let pydoc use the exception instead of sys.exc_info #102830
• gh-102799: use exception instance instead of sys.exc_info() #102885
• gh-102799: use sys.exception() instead of sys.exc_info() in tests #103293
• gh-102799: use sys.exception() instead of sys.exc_info() in pdb #103294
• gh-102799: use sys.exception() instead of sys.exc_info() in contextlib #103311
• gh-102799: replace sys.exc_info by sys.exception in inspect and traceback modules #104032
• gh-102799: replace internal sys.exc_info() call by sys.exception() #106746

[iritkatriel]

Now that 3.10 is out of bugfix mode, we can use sys.exception() (which exists since 3.11, so would not cause issues with normal bugfix backports).