Request based collation fetching (#2621)

* Introduce collation fetching protocol

also move to mod.rs

* Allow `PeerId`s in requests to network bridge.

* Fix availability distribution tests.

* Move CompressedPoV to primitives.

* Request based collator protocol: validator side

- Missing: tests
- Collator side
- don't connect, if not connected

* Fixes.

* Basic request based collator side.

* Minor fix on collator side.

* Don't connect in requests in collation protocol.

Also some cleanup.

* Fix PoV distribution

* Bump substrate

* Add back metrics + whitespace fixes.

* Add back missing spans.

* More cleanup.

* Guide update.

* Fix tests

* Handle results in tests.

* Fix weird compilation issue.

* Add missing )

* Get rid of dead code.

* Get rid of redundant import.

* Fix runtime build.

* Cleanup.

* Fix wasm build.

* Format fixes.

Thanks @andronik !

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

@@ -235,11 +235,11 @@ where
 				}
 			}
 
-			Action::SendRequests(reqs) => {
+			Action::SendRequests(reqs, if_disconnected) => {
 				for req in reqs {
 					bridge
 						.network_service
-						.start_request(&mut bridge.authority_discovery_service, req)
+						.start_request(&mut bridge.authority_discovery_service, req, if_disconnected)
 						.await;
 				}
 			},
@@ -604,7 +604,7 @@ mod tests {
 	use parking_lot::Mutex;
 	use assert_matches::assert_matches;
 
-	use sc_network::Event as NetworkEvent;
+	use sc_network::{Event as NetworkEvent, IfDisconnected};
 
 	use polkadot_subsystem::{ActiveLeavesUpdate, FromOverseer, OverseerSignal};
 	use polkadot_subsystem::messages::{
@@ -681,7 +681,7 @@ mod tests {
 			Box::pin((&mut self.action_tx).sink_map_err(Into::into))
 		}
 
-		async fn start_request<AD: AuthorityDiscovery>(&self, _: &mut AD, _: Requests) {
+		async fn start_request<AD: AuthorityDiscovery>(&self, _: &mut AD, _: Requests, _: IfDisconnected) {
 		}
 	}