* Wrappers classes to dispatch to a backend

* Rework the backend dispatching

- 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

* Dispatch more algorithms and improve auto-test capabilities

* Allow dispatcher decorator without a name

- 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

* Make sphinx pick up backend docs

* make black happy

* Rename decorator to _dispatch as it's experimental

* A few more dispatched functions

* Make convert to and from methods for auto-testing

- Rename `convert` to `convert_from_nx`
- Add `convert_to_nx` function

These will allow backends to return native objects when dispatching,
but provide a mechanism to convert the result to the type expected
by NetworkX tests for the auto-test plugin mechanism.

* More dispatching

* Include name with `convert_**_nx` methods

* Remove known plugin names

This check is not needed, as any plugin can register itself in the entry points section.
The dispatching and auto-testing explicitly specify the plugin to use, so there is no
need to hardcode the options.
These were originally included for security, but any malicious actor would simply use one
of the valid names, so having a hardcoded list does not actually provide any meaningful
security.

* Add `dispatchname` to dispatchable functions

Co-authored-by: Jim Kitchen <jim22k@gmail.com>
Co-authored-by: Erik Welch <erik.n.welch@gmail.com>

* Improve code coverage of cuts

* update tests for cuts

* update doc string description

* update conciseness in tests

* Format code w/ black

* Format docstrings w/ black

* Manual cleanup

* Tell pytest to ignore planned deprecations

* Don't call plt.show during testing

* Another known deprecation

* DOC: rm duplicate line from docstring example

* Minor cleanup

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

* Fixes #3955 (boundary_expansion docs)

* add to docs for steiner_tree

* Add missing functions to docs. Thanks to #4111

* Doc fixups

* Put filters onto the doc pages.

* Add @jamestrimble doc compare script to repo and expand

* Fix latex syntax in docs for trophic

* more latex corrections

* deprecate edge_betweeness and betweeness_centrality_source.

warnings and add to list of deprecations

* Use docs to identify hopcrfot_karo_matching and maximum_matching

* remove  underscore from _naive_greedy_modularity_communities

* cite James Trimble for code that finds missing functions

* Update parallel_betweenness example to avoid deprecated function

betweenness_centrality_source should be replaced by
betweenness_centrality_subset in plot_parallel_betweenness.

find _naive_greedy and change name

* tweak

The copyright and author stuff is not necessary, out-of-date,
and inconsistent.  It takes up visual space and is a pain to
police everyone doing the same thing on the top of the module.

Git handles authorship in a comprehensive and authoritative way.
The LICENSE.txt file applies to all project code.

Change double `` to single ` for all function arguments.
Remove double `` around True, False, None
Leave double `` when a literal python expression is intended.
I found a couple of places where math mode was intended.
Still need to look for those.