Consider using an external library to implement a directed acyclic graph

[eguzki]

#447 introduced Directed Acyclic Graph implementation.

The implementation is not thread-safe.

It implements preventing cycles validation.

It implements indexes on top of the graph to provide API like "give me all nodes labeled as X" used to get all HTTPRoutes or Gateways existing in the graph.

This issue is to consider using other third party implementations that kuadrant can leverage avoiding "reinventing the wheel".

More information from the started discussion here

Candidates we have today, but new candidates may be out there:

• Graph
• dag