Remove dependency on Airbnb ruleset

[jattasNI]

We think it would be a good idea to remove the dependency on the Airbnb ruleset since it makes it more complicated to understand how rules are configured in this repo. There doesn't appear to be much maintenance happening so we feel reasonably convinced that this won't cause us extra work.

We would do this by copying their configurations into our repo and unwinding our overrides. We could also remove configurations that don't apply to NI code like React rules.

We'll need to decide whether to keep their file organization or concatenate them.