Update path_fiddle to use a separate ArtboardInstance per copy

path_fiddle used to advance and draw the same artboard multiple times per frame. This goes against our model where the renderer is allowed to hold a reference on a path and expect it to not mutate between the draw issue and flush. Update path_fiddle to use a separate ArtboardInstance per copy.

Unfortunately, advancing all these separate artboards introduces a 20% (and probably more realistic) performance hit. To get less watered-down raw rendering numbers, we can still use the "pause" feature.

Diffs=

.rive_renderer

@@ -1 +1 @@
-07bc07225ef6ee9e690b09ad8d51d66bbfcd997d
+6cd02abb56a3122c8b4e9d885d81832087dca125