Fix bug where edge colors are randomly shuffled in mpl_draw (#1312)

* Try to make edge_pos iteration deterministic

* Fix minor bug

* Add release note

Author: IvanIsCoding

releasenotes/notes/correct-edge-colors-e082e1761e1c060b.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Fixed a bug introduced in version 0.15 where the edge colors specified as
+    a list in calls to :func:`~rustworkx.visualization.mpl_draw` were not
+    having their order respected. Instead, the order of the colors was
+    being shuffled. This has been restored and now the behavior should
+    match that of 0.14.

rustworkx/visualization/matplotlib.py

@@ -636,9 +636,10 @@ def draw_edges(
         edge_color = "k"
 
     # set edge positions
-    edge_pos = set()
+    edge_pos_keys = dict()
     for e in edge_list:
-        edge_pos.add((tuple(pos[e[0]]), tuple(pos[e[1]])))
+        edge_pos_keys[(tuple(pos[e[0]]), tuple(pos[e[1]]))] = None
+    edge_pos = edge_pos_keys.keys()
 
     # Check if edge_color is an array of floats and map to edge_cmap.
     # This is the only case handled differently from matplotlib