gh-106432: Added WSL support for adjusting the local hostname in smtplib.

This pull request introduces a new functionality to the smtplib library that enables it to detect and handle the Windows Subsystem for Linux (WSL) environment. The main change is the adjustment of the local hostname to ensure compatibility and proper functionality within WSL.

The changes include:

• Addition of code to detect if the environment is WSL and modify the local hostname accordingly
• Documentation updates explaining the purpose, context, and impact of the code
• Clear explanations of the code logic and benefits

These changes enhance the usability and compatibility of smtplib when used within WSL, allowing developers to send emails from applications running on WSL without issues related to the local hostname. The modifications align with the existing codebase and follow the established contribution guidelines.

Please review these changes and consider merging them into the main repository. Thank you!