Expose set original cell index to python

[jorgensd]

To be able to make a valid geometry from Python (without using create_topology, as one wants to avoid re-distribution of data), one has to expose the original_cell_index attribute to Python.
As we have used this as a public variable in C++, I've gone down the route of creating a setter function in the Python binding, rather than exposing a "list-of-lists" to Python, as we would rather like it to be numpy based.

[garth-wells]

Mixed topology support is still highly experimental and under review, so we shouldn’t expose the mixed topology version of original_cell_index yet.

When it’s ready, no need to add a function with ‘set’ in the name. Could be a nanobind read/write property.

[jorgensd]

Mixed topology support is still highly experimental and under review, so we shouldn’t expose the mixed topology version of original_cell_index yet.

When it’s ready, no need to add a function with ‘set’ in the name. Could be a nanobind read/write property.

agreed, much cleaner solution 👍🏻