Add steiner tree functionality to rustworkx-core (#1103)

* Implement deduplicate edge

* Move MetricClousureEdge

* Add definition of _metric_clousure_edges

* Add definition of metric_clousure

* Add definition of fast_metric_edges

* Add definition of steiner_tree

* Add mod steiner_tree to lib.rs

* Add necessary crate

* correct type

* change MetricClousureEdge to generic

* Update steiner_tree

* Finish rustworkx-core port

This commit finishes the rustworkx-core port of the steiner tree and
metric closure functions. In particular this was especially tricky
because the petgraph traits make it exceedingly difficult to have a
generic function that takes in a graph for analysis and modifies it as
most of the traits required for visiting/iteration that are used for
analysis are only defined on borrowed graphs, and the limited traits for
modifying graphs are defined on owned graph types. This causes a
conflict where you can't easily express that a generic type G created in
a function from a user input is both mutated using a trait and analyzed
as there is a type mismatch between G and &G. After spending far too
long to fail to find a pattern to express this, I opted to just use a
discrete type for the return and leave the actual graph mutation up to
the rustworkx-core user because we're lacking the ability to cleanly
express what is needed via petgraph.

* Add back checking on valid weights and terminal nodes

---------

Co-authored-by: Ryuhei Yoshida <[email protected]>

rustworkx-core/src/lib.rs

@@ -92,6 +92,8 @@ mod min_scored;
 pub mod token_swapper;
 pub mod utils;
 
+pub mod steiner_tree;
+
 // re-export petgraph so there is a consistent version available to users and
 // then only need to require rustworkx-core in their dependencies
 pub use petgraph;