Rudder

If we want to accept comments for node properties, we need to first use an internal format that allow to store them. Today, we are using JValue, which is a (very slow) json format.
That format does not allow comments.
We need to change it to hocon ConfigValue to allows to then have the UI to keep comment.

That first step is only backend and should be (almost) iso behavior. The only change is in array overriding in property hierarchy, since hocon replace parent array in place of extending them. Still, other JValue implementation specific behavior can exist, and we should have that code before 6.1 is released since not having it could lead to later breaking change (while now, the hierarchy feature is new and noone relies on its behavior in prod).