Improved Typestability

[behinger]

• removed duplicated function
• make link checker happy
• make linter happy
• generalized the test
• added packages to top
• added precompilation
• type stable designmatrix generation

Related issues

Closes #

Checklist

• [ ] I am following the contributing guidelines
• [ ] Tests are passing
• [ ] Lint workflow is passing
• [ ] Docs were updated and workflow is passing