gh-37775: Add matroid `relabel`
The present PR adds a matroid groundset `relabel` function. It is
optimized for each matroid subclass. It also adds an optional
`groundset` argument to the matroids defined in `database_matroids.py`.
This resolves two `TODO`s left from previous developers.
### :memo: Checklist
- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.
URL: https://github.com/sagemath/sage/pull/37775
Reported by: gmou3
Reviewer(s): gmou3, Matthias Köppe
