Merge PoC Delwaq coupling scripts

[evetion]

The current scripts are still low quality, but do reference existing tables/code that we should test by doing an integration test.

• Make pixi Python environment for coupling
• Create integration test that runs the coupling/delwaq/gen_delwaq.py script.
• Write Ribasim results direct into pointer tabel

[visr]

What is the benefit of a separate pixi environment for this rather than the default one?

[evetion]

For developer purposes it can go into the main one. I was thinking of having coupling as an optional feature to ribasim python you can install with pip, like pip install ribasim[coupling] Not sure if that would align with pixi yet.

[evetion]

Closed by #1137