Parametrize pipe material

[TeyAll]

Description and context

Cable Thermal Model supports circuits with pipes. These pipes can be filled with either water or air. However, the pipe material is not parametrizable. Its thermal properties are hardcoded and based on HDPE material properties. In reality, pipes can be made of other materials than HDPE, such as PVC. This issue aims to allow selection of different pipe materials in the model.

Feature design

The proposed way to implement this feature consists of the following steps.

1. Create a new Enum class PipeMaterial in the enum_classes_cable.py module specifying the materials a pipe can be made of. This class should at least contain the options PE (pcPE) and PVC (pcPVC).
2. Add any missing material properties to material_properties.csv.
3. Add the pipe material to the PipeInputSchema.
4. Create a new attribute pipe_material_df of the Pipe class containing the thermal properties of the pipe material. Add logic to the __init__ method of the Pipe class that reads the thermal properties from material_properties.csv and stores it in a new attribute pipe_material_df of the Pipe class containing the thermal properties of the pipe material. This logic could also be moved to a private setter method that gets called in Pipe.__init__.
5. Adjust the logic in FDCable.get_cable_copy_with_pipe so that the specified material properties are used, instead of the harcoded ones.

Update documentation and tests

As with every change to the code, make sure that documentation is up to date and that the functionality is tested.