Field cancellation maps in a functional label/ROI for EEG/MEG data

Describe the new feature or enhancement

Generate field cancellation maps for a functional label/ROI for EEG and MEG data to understand more about focal vs. widespread cortical patterns.

additional: The role of depth and orientation of dipoles directly at the sulci and gyri patch to understand their influence in focal vs. widespread source patterns. Some sort of plot that shows dipole orientation for individual label would be a nice feature too. This will give a possible alternative idea of a source projection to another i.e., mirror sources.

Describe your proposed implementation

A paper to follow up to implement field cancellation index : https://pubmed.ncbi.nlm.nih.gov/19639553/
additional: Some simulations at the source level, followed by some topography maps at the sensor level.

Additional comments

I think this hasn't been implemented in MNE so far. I would be happy to contribute to the proposal but I need someone to guide me as well as for further discussion.

No file, test, or entry point is named. Start by reading the linked field cancellation index paper and surveying MNE's existing source-level simulation and sensor topography functionality. Done would require an agreed scope, simulations, field cancellation maps for EEG/MEG labels or ROIs, and a decision on whether dipole orientation plots are included.