gh-37788: Add is_graphic/regular
Add naive implementation (through minor checking) of membership checking
functions for two matroid classes (`graphic` and `regular`).
`TODO:` Optimize, and, optionally, return certificates (a graph or a
totally unimodular matrix respectively).
### :memo: Checklist
- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.
### Dependencies
- #37775
URL: https://github.com/sagemath/sage/pull/37788
Reported by: gmou3
Reviewer(s): Matthias Köppe
