Refactor: Abstract Node Info

[aauren]

@jnummelin @rbrtbnfgl @mrueg

This prepares the way for broader refactors in the way that we handle nodes by:

• Separating frequently used node logic from the controller creation steps
• Keeping reused code DRY-er
• Adding interface abstractions for key groups of node data and starting to rely on those more rather than concrete types
• Separating node data from the rest of the controller data structure so that it smaller definitions of data can be passed around to functions that need it rather than always passing the entire controller which contains more data / surface area than most functions need.

Eventually the changes here should better support the work that will need to happen to fix #1738 #676

[aauren]

Refactors are always a bit of a slog to review.

But the gist of this one is that instead of storing all of the physical node data as individual data sets like nodeIPs, nodeIPv4Addrs, nodeHostName, etc. on each of the many kube-router controllers, I moved it into a single abstraction KRNode that now holds all of that data and has appropriate interfaces for only exposing specific subsets based upon need.

The ultimate goal of this refactor is to stop the need of constantly either attaching functions to the main controllers (NetworkServicesController, NetworkRouterController, NetworkPolicyController) or passing the entire controllers around the code base just because functions need a specific subset of data contained on the controllers.

Right now, my mid-term goal is to refactor injectRoute() in order to resolve #1738 in a way that doesn't perpetrate bad coding practices.

But eventually I think that more abstractions are going to be needed like this as there is quite a bit of cruft in the code base.