Refactor the build system

[joaander]

Description

• Use scikit-build-core.
• Assemble a functioning freud package in the build directory.

Motivation and Context

scikit-build-core is more pleasant to work with than scikit-build. However, it still does not provide status messages during successful builds. Therefore, I enabled pure CMake builds to assemble a working package in the build directory. This allows developers to iteratively modify, build, and test freud while observing the build status and not polluting their Python environment.

How Has This Been Tested?

Tested locally on my Mac and Linux workstations.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds or improves functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation improvement (updates to user guides, docstrings, or developer docs)

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [x] I have updated the documentation (if relevant).
• [ ] I have added tests that cover my changes (if relevant).
• [x] All new and existing tests passed.
• [ ] I have updated the credits.
• [ ] I have updated the Changelog.