Add an alternative way of implementing Tauchen's method to `make_tauchen_ar1()`

[QingyuanFang]

By Qingyuan Fang

Please ensure your pull request adheres to the following guidelines:

• [ ] Tests for new functionality/models or Tests to reproduce the bug-fix in code.
• [ ] Updated documentation of features that add new functionality.
• [ ] Update CHANGELOG.md with major/minor changes.