Relax types on DigestItemRef, such that byte slices can be used in addition to vector references (#10536)

* Relax types on `DigestItemRef`, such that byte slices can be used in addition to vector references

* Apply clippy suggestions

substrate/primitives/runtime/src/generic/digest.rs

@@ -177,16 +177,16 @@ pub enum DigestItemRef<'a> {
 	/// the consensus engine can (and should) read them itself to avoid
 	/// code and state duplication.  It is erroneous for a runtime to produce
 	/// these, but this is not (yet) checked.
-	PreRuntime(&'a ConsensusEngineId, &'a Vec<u8>),
+	PreRuntime(&'a ConsensusEngineId, &'a [u8]),
 	/// A message from the runtime to the consensus engine. This should *never*
 	/// be generated by the native code of any consensus engine, but this is not
 	/// checked (yet).
-	Consensus(&'a ConsensusEngineId, &'a Vec<u8>),
+	Consensus(&'a ConsensusEngineId, &'a [u8]),
 	/// Put a Seal on it. This is only used by native code, and is never seen
 	/// by runtimes.
-	Seal(&'a ConsensusEngineId, &'a Vec<u8>),
+	Seal(&'a ConsensusEngineId, &'a [u8]),
 	/// Any 'non-system' digest item, opaque to the native code.
-	Other(&'a Vec<u8>),
+	Other(&'a [u8]),
 	/// Runtime code or heap pages updated.
 	RuntimeEnvironmentUpdated,
 }
@@ -358,8 +358,8 @@ impl<'a> DigestItemRef<'a> {
 			(OpaqueDigestItemId::Seal(w), &Self::Seal(v, s)) |
 			(OpaqueDigestItemId::PreRuntime(w), &Self::PreRuntime(v, s))
 				if v == w =>
-				Some(&s[..]),
-			(OpaqueDigestItemId::Other, &Self::Other(s)) => Some(&s[..]),
+				Some(s),
+			(OpaqueDigestItemId::Other, &Self::Other(s)) => Some(s),
 			_ => None,
 		}
 	}