[Misc] Replace deprecated locale.getdefaultlocale() in diagnose.py

[bluevisor]

Brief Summary

This PR addresses a DeprecationWarning in diagnose.py related to the use of locale.getdefaultlocale(), which is deprecated as of Python 3.15. The warning was as follows:

DeprecationWarning: ‘locale.getdefaultlocale’ is deprecated and slated for removal in Python 3.15. Use setlocale(), getencoding() and getlocale() instead.

Changes Made

• Replaced locale.getdefaultlocale() with a combination of locale.setlocale(locale.LC_ALL, ''), locale.getlocale(), and locale.getpreferredencoding() to fetch locale and encoding information without triggering the deprecation warning.
• Updated the code to format the output similarly to the original function.

Rationale

This change future-proofs the code by using recommended functions (getlocale() and getpreferredencoding()), ensuring compatibility with Python 3.15 and beyond.

Testing

• Verified that the DeprecationWarning no longer appears when running diagnose.py.
• Confirmed that the output format remains consistent with the original implementation.

[feisuzhu]

/rebase