[WIP] Rewriting the Univariate Solver

This PR aims to rewrite a cleaner and robust univariate equation solver.
- [ ] Univariate
    - [x] polynomial
    - [x] rational
    - [ ] trigonometric
    - [ ] functions with exp and log
- [ ] Multivariate
The equation has no general real solution `log(y)` isn't real for negative `y` hence returned an `EmptySet()`