import xgi takes a long time

[nwlandry]

In a Jupyter Notebook (In editable mode) it can take up to 10s to run import xgi. Maybe lazy loading would solve this problem? NetworkX seems to have some of this functionality.

[kaiser-dan]

Alongside the changes from #675, the upcoming lazy keyword may be a good fix for this. The standard library implementation will be coming in Python 3.15, however; should we add a more bespoke lazy importing system for Python <= 3.14?