Update YOLOv8 Dependency Management and Import Path

[ng-fukgin]

This pull request aims to update the YOLOv8 project's installation and dependency management process in accordance with the latest PEP 517 and PEP 518 standards. Additionally, based on the discussion in Issue #14, I have updated the import path for the select_device function. These changes are intended to simplify the installation process, make dependency management more standardized and maintainable, and ensure compatibility with the latest version of the code.

The specific changes are as follows:

• Adopting the pyproject.toml file, and using pip (version 19.0 or higher) to run the installation command directly in the project's root directory, automatically installs the project and its dependencies. This simplifies the installation process and improves the standardization and maintainability of dependency management.
• The import path for the select_device function has been updated from ultralytics.yolo.utils.torch_utils to ultralytics.utils.torch_utils to ensure compatibility with the project's latest structure, making the code clearer, easier to understand, and maintain.

These updates aim to improve the overall quality and user experience of the project.