Align node markers with existing software

[visr]

We currently use these icons for the different node types:

The image above are the QGIS QML markers defined here:
https://github.com/Deltares/Ribasim/blob/v2025.2.0/python/ribasim/ribasim/styles/NodeStyle.qml
We also have icons defined for Ribasim Python's model.plot(), they are defined separately but made to appear the same:
https://github.com/Deltares/Ribasim/blob/v2025.2.0/python/ribasim/ribasim/geometry/node.py#L105-L141

The design of these markers has grown organically and has not received too much thought. For node types that are similar to node types in SOBEK or D-Hydro, it would make sense to align where possible. Many users of these software package can dream these icons, and offering familiar icons will help them understand models.

Even if we decide to not align, it would be good to review the markers, as for instance LevelBoundary and Outlet are very hard to distinguished. And ideally verify that they can be distinguished by colorblind people.