approval-voting improvement: include all tranche0 assignments in one certificate (#1178)

**_PR migrated from https://github.com/paritytech/polkadot/pull/6782_** 

This PR will upgrade the network protocol to version 3 -> VStaging which
will later be renamed to V3. This version introduces a new kind of
assignment certificate that will be used for tranche0 assignments.
Instead of issuing/importing one tranche0 assignment per candidate,
there will be just one certificate per relay chain block per validator.
However, we will not be sending out the new assignment certificates,
yet. So everything should work exactly as before. Once the majority of
the validators have been upgraded to the new protocol version we will
enable the new certificates (starting at a specific relay chain block)
with a new client update.

There are still a few things that need to be done:

- [x] Use bitfield instead of Vec<CandidateIndex>:
https://github.com/paritytech/polkadot/pull/6802
  - [x] Fix existing approval-distribution and approval-voting tests
  - [x] Fix bitfield-distribution and statement-distribution tests
  - [x] Fix network bridge tests
  - [x] Implement todos in the code
  - [x] Add tests to cover new code
  - [x] Update metrics
  - [x] Remove the approval distribution aggression levels: TBD PR
  - [x] Parachains DB migration 
  - [x] Test network protocol upgrade on Versi
  - [x] Versi Load test
  - [x] Add Zombienet test
  - [x] Documentation updates
- [x] Fix for sending DistributeAssignment for each candidate claimed by
a v2 assignment (warning: Importing locally an already known assignment)
 - [x]  Fix AcceptedDuplicate
 - [x] Fix DB migration so that we can still keep old data.
 - [x] Final Versi burn in

---------

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
Co-authored-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

polkadot/node/network/bitfield-distribution/src/lib.rs

@@ -25,14 +25,15 @@
 use always_assert::never;
 use futures::{channel::oneshot, FutureExt};
 
+use net_protocol::filter_by_peer_version;
 use polkadot_node_network_protocol::{
 	self as net_protocol,
 	grid_topology::{
 		GridNeighbors, RandomRouting, RequiredRouting, SessionBoundGridTopologyStorage,
 	},
 	peer_set::{ProtocolVersion, ValidationVersion},
-	v1 as protocol_v1, v2 as protocol_v2, OurView, PeerId, UnifiedReputationChange as Rep,
-	Versioned, View,
+	v1 as protocol_v1, v2 as protocol_v2, vstaging as protocol_vstaging, OurView, PeerId,
+	UnifiedReputationChange as Rep, Versioned, View,
 };
 use polkadot_node_subsystem::{
 	jaeger, messages::*, overseer, ActiveLeavesUpdate, FromOrchestra, OverseerSignal, PerLeafSpan,
@@ -101,6 +102,11 @@ impl BitfieldGossipMessage {
 					self.relay_parent,
 					self.signed_availability.into(),
 				)),
+			Some(ValidationVersion::VStaging) =>
+				Versioned::VStaging(protocol_vstaging::BitfieldDistributionMessage::Bitfield(
+					self.relay_parent,
+					self.signed_availability.into(),
+				)),
 			None => {
 				never!("Peers should only have supported protocol versions.");
 
@@ -131,9 +137,9 @@ pub struct PeerData {
 
 /// Data used to track information of peers and relay parents the
 /// overseer ordered us to work on.
-#[derive(Default, Debug)]
+#[derive(Default)]
 struct ProtocolState {
-	/// Track all active peers and their views
+	/// Track all active peer views and protocol versions
 	/// to determine what is relevant to them.
 	peer_data: HashMap<PeerId, PeerData>,
 
@@ -492,17 +498,13 @@ async fn relay_message<Context>(
 	} else {
 		let _span = span.child("gossip");
 
-		let filter_by_version = |peers: &[(PeerId, ProtocolVersion)],
-		                         version: ValidationVersion| {
-			peers
-				.iter()
-				.filter(|(_, v)| v == &version.into())
-				.map(|(peer_id, _)| *peer_id)
-				.collect::<Vec<_>>()
-		};
+		let v1_interested_peers =
+			filter_by_peer_version(&interested_peers, ValidationVersion::V1.into());
+		let v2_interested_peers =
+			filter_by_peer_version(&interested_peers, ValidationVersion::V2.into());
 
-		let v1_interested_peers = filter_by_version(&interested_peers, ValidationVersion::V1);
-		let v2_interested_peers = filter_by_version(&interested_peers, ValidationVersion::V2);
+		let vstaging_interested_peers =
+			filter_by_peer_version(&interested_peers, ValidationVersion::VStaging.into());
 
 		if !v1_interested_peers.is_empty() {
 			ctx.send_message(NetworkBridgeTxMessage::SendValidationMessage(
@@ -515,7 +517,15 @@ async fn relay_message<Context>(
 		if !v2_interested_peers.is_empty() {
 			ctx.send_message(NetworkBridgeTxMessage::SendValidationMessage(
 				v2_interested_peers,
-				message.into_validation_protocol(ValidationVersion::V2.into()),
+				message.clone().into_validation_protocol(ValidationVersion::V2.into()),
+			))
+			.await
+		}
+
+		if !vstaging_interested_peers.is_empty() {
+			ctx.send_message(NetworkBridgeTxMessage::SendValidationMessage(
+				vstaging_interested_peers,
+				message.into_validation_protocol(ValidationVersion::VStaging.into()),
 			))
 			.await
 		}
@@ -540,6 +550,10 @@ async fn process_incoming_peer_message<Context>(
 		Versioned::V2(protocol_v2::BitfieldDistributionMessage::Bitfield(
 			relay_parent,
 			bitfield,
+		)) |
+		Versioned::VStaging(protocol_vstaging::BitfieldDistributionMessage::Bitfield(
+			relay_parent,
+			bitfield,
 		)) => (relay_parent, bitfield),
 	};
 
@@ -774,9 +788,11 @@ async fn handle_network_msg<Context>(
 				handle_peer_view_change(ctx, state, new_peer, old_view, rng).await;
 			}
 		},
-		NetworkBridgeEvent::PeerViewChange(peerid, new_view) => {
-			gum::trace!(target: LOG_TARGET, ?peerid, ?new_view, "Peer view change");
-			handle_peer_view_change(ctx, state, peerid, new_view, rng).await;
+		NetworkBridgeEvent::PeerViewChange(peer_id, new_view) => {
+			gum::trace!(target: LOG_TARGET, ?peer_id, ?new_view, "Peer view change");
+			if state.peer_data.get(&peer_id).is_some() {
+				handle_peer_view_change(ctx, state, peer_id, new_view, rng).await;
+			}
 		},
 		NetworkBridgeEvent::OurViewChange(new_view) => {
 			gum::trace!(target: LOG_TARGET, ?new_view, "Our view change");