babe: make secondary slot randomness available on-chain (#7053)

* babe: make secondary slot randomness available on-chain

* babe: extract out vrf_output function

* babe: add missing comment

* babe: fix incorrectly storing primary randomness

* babe: add test for onchain author vrf

* babe: fix reviewer nits

* runtime: bump spec_version

* babe: remove outer Option for AuthorVrfRandomness

* babe: fix reviewer nits on doc strings

* babe: move make_vrf_output to mock.rs

* babe: cleanup docs

* babe: kill ephemeral entry instead of take

* babe: use type alias for maybe randomness

Co-authored-by: André Silva <andrerfosilva@gmail.com>

substrate/bin/node/runtime/src/lib.rs

@@ -112,8 +112,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to 0. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 259,
-	impl_version: 1,
+	spec_version: 260,
+	impl_version: 0,
 	apis: RUNTIME_API_VERSIONS,
 	transaction_version: 1,
 };