feat: add pyoptinterface io_api

[coroa]

Changes proposed in this Pull Request

Adds an alternative io_api="poi" option, which uses pyoptinterface to communicate the optimisation problem directly to the solvers.

Initial testing is quite promising for gurobi, comparable speed on large instances, faster on small ones (for highs the effects are limited).

Checklist

• 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.

[metab0t]

For highs, you can also use set_raw_parameter: https://github.com/metab0t/PyOptInterface/blob/b3e1f455885de5734f42ccdfbd70827b638110fb/src/pyoptinterface/_src/highs.py#L419

[coroa]

POI is slower than lp-polars on large instances and slower than direct on small instances and selective in-place model updates are slow too. So, we'll most likely close this PR and focus on improving the direct models instead.

[FabianHofmann]

closing this by #630