Add encapsulation dag functionality

[tlarock]

This PR adds a new file for constructing encapsulation DAGs of hypergraphs with three different kinds of relations as discussed in #413, as well as tests. Builds on #427.

I've exposed two functions:

1. to_encapsulation_dag(H, subset_types="all"). Computes and returns an encapsulation DAG of the hypergraph H. The parameter subset_types controls the types of relations that are included in the DAG.
2. empirical_subsets_filter(H, dag). Filters dag of H in place from all subset relations to only empirically maximum relations. Used internally in to_encapsulation_dag(H, subset_type="empirical"). Exposed externally so that a user can first compute and store the full DAG, then apply filtering later to a copy, i.e.:

H = xgi.Hypergraph(incoming_data=[["a","b","c"], ["b","c","f"], ["a","b"], ["c", "e"], ["a"], ["f"]])
dag = to_encapsulation_dag(H, subset_type="all")
dag.edges()
OutEdgeView([(0, 2), (0, 4), (2, 4), (1, 5)])
empirical_subsets_filter(H, dag)
dag.edges()
OutEdgeView([(0, 2), (2, 4), (1, 5)])

dag = to_encapsulation_dag(H, subset_types="empirical")
dag.edges()
OutEdgeView([(0, 2), (2, 4), (1, 5)])

Happy to clarify anything or take suggestions for changes!

[codecov]

Codecov Report

Patch coverage: 95.16% and project coverage change: +0.06% 🎉

Comparison is base (52e6aac) 90.97% compared to head (dd17340) 91.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #444      +/-   ##
==========================================
+ Coverage   90.97%   91.03%   +0.06%     
==========================================
  Files          59       60       +1     
  Lines        4100     4162      +62     
==========================================
+ Hits         3730     3789      +59     
- Misses        370      373       +3     

Files Changed	Coverage Δ
xgi/convert/encapsulation_dag.py	95.08% <95.08%> (ø)
xgi/convert/__init__.py	100.00% <100.00%> (ø)

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[maximelucas]

Thanks Tim! I think the new functions still need to be added to the docs?
I'll continue reviewing this later today or tomorrow.

[maximelucas]

Looks good to me, thanks Tim! Just a few minor comments.

Also, do you think you could add short examples if not too long? Otherwise it's fine.

[tlarock]

Ready to go on my end now :)