Let's make the ResizeFeaturesBase constructor package scope, which would remove it from the public API. There seems to be no good reason for the constructor to be public, since we really don't want to allow arbitrary subclassing.

This suggests that we might want to file a bug to deprecate the constructor for removal in 20 and remove it (i.e., make it package scope) in 21.

This ticket is for making the constructor package protected.
This comes from work done for alternative column resize policy JDK-8293119.