Add scaling

[davide-f]

Closes # (if applicable).

Changes proposed in this Pull Request

This PR aims to showcase a possible implementation of scaling into linopy.
Scaling of mathematical problems is complex and different solvers adopt different standards (if any). Generally, it is up to the modeller to cast the problem within adeguate ranges. This PR may give an intermediate tool to answer this problem.

The idea is to add a scaling parameter to each variable, constraint and objective term that will be used to scale the problem accordingly.
Scaling applied to each variable divides all coefficients of the variable column-wise, while scaling applied to constraints or the objective apply the scaling row-wise.

This PR is being used for testing the role of scaling and showcase a possible implementation.

Checklist

• AI-generated content is marked (see AGENTS.md).
• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Unit tests for new features were added (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the MIT license.