Use the grading client for utils files

[HuangJunye]

We often need to include utils files for coding challenges. Currently these files are stored with the notebooks, for example, in QDC 2024 Day 1 challenge: https://github.com/qiskit-community/qdc-challenges-2024/tree/main/Day_1/utils.

We should move those files to the grading client for these reasons:

1. The client often need to include those same files for grading, anyway. See for example: Include data needed for grading in setup.py #185
2. Importing the files / codes from the grading client will make sure these files are exactly the same. See for example here: qiskit-community/qdc-challenges-2024@1ab7f18, the circuit written in the notebook doesn't match the circuit used for grading