Add sparse support to multigraph LCC functions

[bdpedigo]

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What does this implement/fix? Briefly explain your changes.

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[bdpedigo]

@nyecarr you mentioned sparse omni the other day, I think fixing this will be necessary as part of that workflow

[asaadeldin11]

looks like theres some formatting issues but the rest looks fine to me.

[daxpryce]

formatting issues are probably because of isort

[bdpedigo]

@daxpryce it looks like the functions multigraph_lcc_intersection and multigraph_lcc_union claim they support lists of networkx graphs (e.g. here: https://github.com/microsoft/graspologic/blob/e5d896d3798aca526d592d4925c7f8be27e7b622/graspologic/utils/utils.py#L643) but in reality, they don't (e.g. here: https://github.com/microsoft/graspologic/blob/e5d896d3798aca526d592d4925c7f8be27e7b622/graspologic/utils/utils.py#L670)

I was in the process of adding sparse support in this PR when I came across this - I wonder whether you all have any use for these things working on networkx or not? If not, we could just take out of our contract with the user for now?

[bdpedigo]

note that I think y'all care about this functionality (which I believe you reimplemented here https://github.com/microsoft/graspologic/blob/e5d896d3798aca526d592d4925c7f8be27e7b622/graspologic/pipeline/embed/omnibus_embedding.py#L162), not that I am necessarily advocating for these util functions to support networkx

[bdpedigo]

decision from talk on 12/14: just make this accept AdjacencyMatrix or whatever, no nx for now