Aura: Skip initialize block & remove cache (#9132)

This instructs the Aura runtime api to skip initialize block, when
requesting the authorities. This is important, as we don't want to use
the new authorities that should be used from the next block on.
Besides that, it removes the caching stuff. The cache is not available
on full nodes anyway. In the future we should store the authorities
probably in the aux store.

substrate/client/consensus/aura/src/import_queue.rs

@@ -317,43 +317,6 @@ impl<B: BlockT, C, P, CAW, CIDP> Verifier<B> for AuraVerifier<C, P, CAW, CIDP> w
 	}
 }
 
-fn initialize_authorities_cache<A, B, C>(client: &C) -> Result<(), ConsensusError> where
-	A: Codec + Debug,
-	B: BlockT,
-	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + UsageProvider<B>,
-	C::Api: AuraApi<B, A>,
-{
-	// no cache => no initialization
-	let cache = match client.cache() {
-		Some(cache) => cache,
-		None => return Ok(()),
-	};
-
-	let best_hash = client.usage_info().chain.best_hash;
-
-	// check if we already have initialized the cache
-	let map_err = |error| sp_consensus::Error::from(sp_consensus::Error::ClientImport(
-		format!(
-			"Error initializing authorities cache: {}",
-			error,
-		)));
-
-	let block_id = BlockId::hash(best_hash);
-	let authorities: Option<Vec<A>> = cache
-		.get_at(&well_known_cache_keys::AUTHORITIES, &block_id)
-		.unwrap_or(None)
-		.and_then(|(_, _, v)| Decode::decode(&mut &v[..]).ok());
-	if authorities.is_some() {
-		return Ok(());
-	}
-
-	let authorities = crate::authorities(client, &block_id)?;
-	cache.initialize(&well_known_cache_keys::AUTHORITIES, authorities.encode())
-		.map_err(map_err)?;
-
-	Ok(())
-}
-
 /// Should we check for equivocation of a block author?
 #[derive(Debug, Clone, Copy)]
 pub enum CheckForEquivocation {
@@ -438,8 +401,6 @@ pub fn import_queue<'a, P, Block, I, C, S, CAW, CIDP>(
 	CIDP: CreateInherentDataProviders<Block, ()> + Sync + Send + 'static,
 	CIDP::InherentDataProviders: InherentDataProviderExt + Send + Sync,
 {
-	initialize_authorities_cache(&*client)?;
-
 	let verifier = build_verifier::<P, _, _, _>(
 		BuildVerifierParams {
 			client,