Add notes to `ImportError` for common issues

Feature or enhancement

Proposal:

ImportErrors are very common, and almost always dependent on the interpreter initialization and/or environment setup. There are many common issues we could try to detect, and give users hints on the possible cause.

• Failing to load native modules when a module for a different ABI is available
  • Eg. https://github.com/python/cpython/issues/127294#issuecomment-2501787837
    • A .cp313t-win_amd64.pyd module is available, but we were looking for .cp313-win_amd64.pyd
• Failing to import a non-stdlib module with the site initialization disabled (-S)
• Failing to import a module available in the user site-packages with the user site initialization disabled (-s)
• Failing to import a module available in . with PYTHONSAFEPATH/-P enabled
• Failing to import a module when ignoring PYTHON* environment variables (-E) but PYTHONPATH or PYTHONHOME are set (which users might be relying on)
• (suggest more!)

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-136817
• gh-136821

Issue にはソースファイルやテストが記載されていません。まずリンクされている PR gh-136817 と gh-136821 を確認し、その後、選択した環境ケースに関係する ImportError の処理を追跡してください。合意したケースについて役立つ注記を追加してテストすれば完了です。