Performance of elemental_data

[roosre]

🔍 Before submitting the issue

• I have searched among the existing issues

🐞 Description of the bug

Accessing the elemental data in a huge model takes seconds.

Mainly because all data is collected at once.

✅ Expected behavior

Retrieving data should be much more efficient

📝 Steps to reproduce

Open a huge model (ask René if you don't have one)
Ensure that the model is up-to-date (model.update())
access elemental data of a ply with many elements (ply.elemental_data)

📃 Relevant log output

None

[greschd]

Related: #410