[Feat] Add DACT and NeuOpt Improvement Models

[yining043]

Description

• Add k-opt env for TSP.
• Add DACT and NeuOpt models.
• Enhance the support for improvement methods.

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• [x] New feature (non-breaking change which adds core functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

Go over all the following points, and put an x in all the boxes that apply. If you are unsure about any of these, don't hesitate to ask. We are here to help!

• [x] My change requires a change to the documentation.
• [x] I have updated the tests accordingly (required for a bug fix or a new feature).
• [ ] I have updated the documentation accordingly.

[fedebotu]

Awesome! No more comments, I think ready to merge @cbhua at your will