Simplify BABE pre-digest definitions (#5289)

* Init vrf crate without type alias

* Generic PreDigest definition for BABE

* Fix BABE vrf interface change

* Missing default-features def in sp-consensus-babe

* Fix sp-consensus-babe compile

* frame-babe: fix type inference

* Unify type definitions of vrf output/proof and randomness

* frame-babe: fix tests

* Bump node impl version

* Update cargo lock

* Derive Copy for RawVRFOutput and RawVRFProof

* Fix duplicated derive

Co-authored-by: Gavin Wood <gavin@parity.io>

substrate/primitives/consensus/babe/src/lib.rs

@@ -22,6 +22,10 @@
 pub mod digests;
 pub mod inherents;
 
+pub use sp_consensus_vrf::schnorrkel::{
+	Randomness, VRF_PROOF_LENGTH, VRF_OUTPUT_LENGTH, RANDOMNESS_LENGTH
+};
+
 use codec::{Encode, Decode};
 use sp_std::vec::Vec;
 use sp_runtime::{ConsensusEngineId, RuntimeDebug};
@@ -50,12 +54,6 @@ pub type AuthorityId = app::Public;
 /// The `ConsensusEngineId` of BABE.
 pub const BABE_ENGINE_ID: ConsensusEngineId = *b"BABE";
 
-/// The length of the VRF output
-pub const VRF_OUTPUT_LENGTH: usize = 32;
-
-/// The length of the VRF proof
-pub const VRF_PROOF_LENGTH: usize = 64;
-
 /// The length of the public key
 pub const PUBLIC_KEY_LENGTH: usize = 32;
 
@@ -115,7 +113,7 @@ pub struct BabeConfiguration {
 	pub genesis_authorities: Vec<(AuthorityId, BabeAuthorityWeight)>,
 
 	/// The randomness for the genesis epoch.
-	pub randomness: [u8; VRF_OUTPUT_LENGTH],
+	pub randomness: Randomness,
 
 	/// Whether this chain should run with secondary slots, which are assigned
 	/// in round-robin manner.