py2neo now EOL

[dotsdl]

py2neo is now EOL: neo4j-contrib/py2neo@7f57cbe

We had observed relative inactivity, but the object model provided by py2neo made it much easier to do translation from gufe to Neo4j and back than the official Python driver would have. It is unclear at this time what the best course of action is.

Possible actions include:

• refactor out use of py2neo and switch to use of official Python driver, add in abstractions where needed to translate objects from gufe to Neo4j representations
• fork py2neo and keep it on life support

It may be worth considering what to do next in the context of #118.

[dotsdl]

@ianmkenney assigning this one to you, since it may be necessary to move to Neo4j 5.x to solve #121, and moving to Neo4j 5.x will require removal of py2neo in favor of the official Python driver only.

[ianmkenney]

#235 partially addresses this issue. It removes py2neo as communication layer between alchemiscaleand the Neo4j database, but still uses the Subgraph machinery for dealing with gufe and networkx objects.

The next step is to replace Subgraph, Node, Relationship, and various query generators with our own classes and functions. From there we should be able to cut out py2neo completely.