- Name is taken from the decorated function
- Raise error if backend doesn't implement a decorated function which is called
- Check for duplicate names for dispatching algorithms

- Use __networkx_plugin__=name to find graph-like objects instead of
  subclassing
- Add PluginInfo to smooth over differences in importlib.metadata across
  python versions
- Add dispatch behavior override via environment variable to aid in
  testing plugins

* Update deprecation todo list

* Remove silenced warnings

* Split MGG test into two based on dependencies.

* Parametrize tests on prime numbers.

* Use fns from nx namespace, rm explicit imports.

* Parametrize exception test and check message.

* Fixed test for average shortest path in the case of directed graphs

* Fixed order

* Update networkx/algorithms/shortest_paths/tests/test_generic.py

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

* Release bullet; added versionchanged

* Add brief description to versionchanged directive.

* Fixed definition

* Using \substack

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>