EvoXTorch project structure changes

[BillHuang2001]

Description

Major Breaking Changes:

1. Adopted src-layout:
   The project structure has been reorganized to use a src/evox/... layout, enabling the packaging of the library.

2. New Testing Framework:

   • Converted individual test programs into unittest classes for better structure and scalability.
   • Tests and benchmarks have been separated. Benchmark programs are now located in the benchmarks/ directory, where they can perform large-scale computations and include profiling functionality.

Minor Changes

• Update the CI/CD, it should now install torch and run tests with unittest.
• Add ruff check action.
• Add pre-commit config.

Checklist

• I have formatted my Python code with ruff.
• I have good commit messages.
• If adding new algorithms, problems, operators:
  • Added related test cases.
  • Added docstring to explain important parameters.
  • Added entries in the docs.

[BillHuang2001]

Ready for review.

[BillHuang2001]

• Brax is now converted to src-layout.
• Related tests are converted to unittest.
• Format code.

[sses7757]

I have reviewed all codes and tests. The documentation can be added in future PRs.