babe: secondary blocks with VRF (#5501)

* babe: secondary blocks with VRF

* Fix node runtime compile

* Fix test-utils runtime interface

* Fix babe tests

* typo: v == 2

* babe: support online configuration upgrades

* Fix rpc tests

* Fix runtime version tests

* Switch to use NextConfigDescriptor instead of changing runtime interface

* Fix tests

* epoch-changes: map function that allows converting with different epoch types

* Add migration script for the epoch config change

* Fix docs for PrimaryAndSecondaryVRFSlots

* Add docs of `SecondaryVRF` in babe crate

* babe-primitives: Secondary -> SecondaryPlain

* babe-client: Secondary -> SecondaryPlain

* Fix migration tests

* test-utils-runtime: Secondary -> SecondaryPlain

* Fix missing name change in test-utils-runtime

* Fix migration: Epoch should be EpochV0

* Update client/consensus/babe/src/lib.rs

Co-Authored-By: André Silva <[email protected]>

* Fix new epochChanges version

* Fix babe-primitives naming changes

* Fix merge issues in babe-client

Co-authored-by: André Silva <[email protected]>
Co-authored-by: André Silva <[email protected]>