Bad exposure of PropertyFieldsContainer

[PProfizi]

Before submitting the issue

• I have checked for Compatibility issues
• I have searched among the existing issues
• I am using a Python virtual environment

Description of the bug

While investigating why some input types do not render properly in the documentation (see here), I realized it is because they were recently changed to type DpfTypeCollection<CPropertyField> instead of CPropertyField. The problem is that the PropertyFieldsContainer or PropertyFieldCollection is not an actually available type in PyDPF.
All we have is a mock-up class created because it seems like we did not want to expose a PropertyFieldsContainer type.
Now that an operator requires it though, we need to properly expose it in PyDPF, most likely using the CollectionFactory.
The code generation scripts also need to now understand the DpfTypeCollection in a pin spec and translate it to the right PyDPF collection type.

Steps To Reproduce

https://dpf.docs.pyansys.com/version/stable/api/ansys.dpf.core.operators.utility.merge_weighted_fields_containers.html

Which Operating System causes the issue?

Windows

Which DPF/Ansys version are you using?

DPF Server 2025.2.pre0

Which Python version causes the issue?

3.11

Installed packages

NA

[PProfizi]

@rafacanton FYI