Test smart_holder in virtual inheritance

[MannixYang]

Description

This is a Test PR.
Related issues #5786 .
The error occurred at Visual Studio 17 2022 X64.

Suggested changelog entry:

• Placeholder.

[rwgk]

After you push the clang-tidy fix (remove the redundant virtual), could you please mark this PR as "Ready for review"? That's the trick to get the full CI matrix.

[rwgk]

From

https://chatgpt.com/share/689ee2ee-514c-8008-9d6b-2566dec08a6e

"the reproducer only triggers under MSVC x64"

@MannixYang Did you already try to get a backtrace? That'll probably help enormously in homing in on the root cause. (ChatGPT has a few guesses.)

[MannixYang]

@rwgk Sorry for replying to you so late.
I can't even catch the exception using try-except. Is there any other better way to get the backtrace in pybind11-test.

def test_animals():
    tiger = m.Tiger()
    try:
        tiger.clone()
    except Exception as e:
        pass