feat: add set_logging_level functionality

[pranayyb]

Description

Added a utility function set_logging_level to configure the global pruna_logger logging level programmatically or via the PRUNA_LOG_LEVEL environment variable. Also added unit tests to verify correct behavior for valid and invalid logging levels.

Related Issue

Fixes #351

Type of Change

• New feature

How Has This Been Tested?

• Programmatically setting logging levels (DEBUG, INFO, WARNING, ERROR, CRITICAL)
• Setting logging levels via environment variable (PRUNA_LOG_LEVEL)
• Validation that invalid logging levels raise ValueError
• All tests pass locally using pytest

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my feature works
• New and existing unit tests pass locally with my changes

Additional Notes

• Default logging level is INFO if none is provided and environment variable is not set.
• Function raises a clear error message if an invalid logging level is passed.

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Note

Introduce set_logging_level to configure pruna_logger (programmatically or via PRUNA_LOG_LEVEL) and add tests for valid/invalid levels.

• Logging:
  • Add set_logging_level in src/pruna/logging/logger.py to configure pruna_logger via argument or PRUNA_LOG_LEVEL env var; validates against supported levels and applies at import.
• Tests:
  • Add tests/config/test_logging.py covering programmatic level setting, env-based setting, and invalid level error handling.

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[johannaSommer]

LGTM, thanks a lot @pranayyb