Add BFS-based Regular Path Query Algorithm

[georgiy-belyanin]

The BFS-based Regular Path Query Algorithm is one of baseline algorithms we want to compare with. Currently, it is a part of LAGraph. It should be supported as one way to evaluate regular path queries.

That is, the possible pipeline is:

• User types a query, e.g. a SPARQL query ?x <label> <node>.
• Pathrex parses it.
• Pathrex builds an AST.
• Pathrex builds NFA and gets its adjacency matrix decomposition by label somehow from the AST.
• Pathrex runs LAGraph_RegularPathQuery() on the loaded graph.

For more information refer to the corresponding LSGDA paper.