Request based PoV distribution (#2640)

* Indentation fix.

* Prepare request-response for PoV fetching.

* Drop old PoV distribution.

* WIP: Fetch PoV directly from backing.

* Backing compiles.

* Runtime access and connection management for PoV distribution.

* Get rid of seemingly dead code.

* Implement PoV fetching.

Backing does not yet use it.

* Don't send `ConnectToValidators` for empty list.

* Even better - no need to check over and over again.

* PoV fetching implemented.

+ Typechecks
+ Should work

Missing:

- Guide
- Tests
- Do fallback fetching in case fetching from seconding validator fails.

* Check PoV hash upon reception.

* Implement retry of PoV fetching in backing.

* Avoid pointless validation spawning.

* Add jaeger span to pov requesting.

* Add back tracing.

* Review remarks.

* Whitespace.

* Whitespace again.

* Cleanup + fix tests.

* Log to log target in overseer.

* Fix more tests.

* Don't fail if group cannot be found.

* Simple test for PoV fetcher.

* Handle missing group membership better.

* Add test for retry functionality.

* Fix flaky test.

* Spaces again.

* Guide updates.

* Spaces.

polkadot/node/network/bridge/src/network.rs

@@ -237,14 +237,14 @@ impl Network for Arc<NetworkService<Block, Hash>> {
 			Recipient::Peer(peer_id) =>  Some(peer_id),
 			Recipient::Authority(authority) =>
 				authority_discovery
-				.get_addresses_by_authority_id(authority)
-				.await
-				.and_then(|addrs| {
-					addrs
-						.into_iter()
-						.find_map(|addr| peer_id_from_multiaddr(&addr))
-				}),
-			};
+					.get_addresses_by_authority_id(authority)
+					.await
+					.and_then(|addrs| {
+						addrs
+							.into_iter()
+							.find_map(|addr| peer_id_from_multiaddr(&addr))
+					}),
+		};
 
 		let peer_id = match peer_id {
 			None => {