feat(run.py): enhance code execution cog with improved error handling and documentation

Add comprehensive docstrings to functions and classes for better
understanding and maintainability. Introduce custom exceptions for
specific error scenarios like missing code, invalid format, unsupported
language, and compilation errors. Refactor code to improve readability
and maintainability by using helper functions and constants. Enhance
user feedback with detailed error messages and usage instructions.

These changes improve the robustness and user experience of the code
execution cog by providing clear error messages and documentation,
making it easier for users to understand how to use the feature and for
developers to maintain and extend the code.

Author: kzndotsh