This is a maintenance change to move the private validator package out
of the types and to a top-level location. There is no good reason to
keep it under the types and it will more clearly coommunicate where
additions related to the privval belong. It leaves the interface and the
mock in types for now as it would introduce circular dependency between
privval and types, this should be resolved eventually.
* mv priv_validator to privval pkg
* use consistent `privval` as import
Follow-up to #1255
Anton Kaliaev
Ethan Buchman
Liamsi
Alexander Simmerl