Graph property recognition algorithms

I'd like to add the following graph property recognition algorithms to Graphs.jl:

• is_cartesian_product (Imrich and Peterin 2007)
• is_chordal (Tarjan and Yannakakis 1984)
• is_chordal_bipartite + is_strongly_chordal (Spinrad 1993)
• is_cograph(Habib and Paul 2005)
• is_outerplanar (Wiegers 1986)
• is_planar (de Fraysseix and Rosenstiehl 1982)

All of these are algorithms implemented in SageMath that I regularly use in my research, and which I typically have to reimplement from scratch or use my own FFI with sage to access from Julia. Given that Graphs.jl already includes functions such as is_bipartite, is_cyclic, is_strongly_connected, etc., I think (at least some of) these algorithms would be well-suited for inclusion.

Should the maintainers deem these additions appropriate, I believe each item listed above merits its own separate PR to avoid overloading any single review.

Start by reading the existing Graphs.jl predicates such as is_bipartite, is_cyclic, and is_strongly_connected, then consult the cited papers and corresponding SageMath implementations. Treat each requested predicate as a separate PR; done means one selected algorithm is included in Graphs.jl with behavior matching its specification.