Allow saving and loading the 3D grid to and from an HDF5 file

[elenafuengar]

📝 Pull Request Summary

To close #32, added new functions that allow to save and load the generated grid with the imported solids STL masks to and from an HDF5 file, saving valuable time in parametric studies.

🔧 Changes Made

• Add save_to_h5 and load_from_h5 routines to GridFIT3D to enable grid saving to HDF5 and grid reconstruction from HDF5.
• Refactored GridFIT3D constructor __init__ to allow 3 grid initialization methods: from domain bounds and number of cells (legacy) from x, y, z numpy arrays or from HDF5 previously saved file.
• Style enhancements using RUFFs linter in examples, and core filesGridFIT3D, SolverFIT3D, routines.py, WakeSolver
• Improvements in WakeSolver load results, now updating folder name in self or taking self.folder if passed to constructor. Ez_file is now set to None in constructor, and default is self.folder+'Ez.h5'.
• Added load and save grid tests to 001
• Added load and save grid to notebooks 002 and 006
• Added domain bounds to Logger and updated test 007 to compare the dicts using np.isclose instead of ==, working now also for MPI runs.
• minor build changes to pyproject.toml needed for the new functions to work
• Introduced new PR workflow to run MPI tests automatically on PR update.

✅ Checklist

• Code follows the project's style and guidelines
• Added tests for new functionality --> added in test 001 (both save and load)
• Updated documentation (mentioned in docs/ or included in examples/ and notebooks/) --> added to notebook 002 and 006.
• Verified that changes do not break existing functionality (automatic tests passing): both CPU and MPI

📌 Related Issues / PRs

Closes #32