Integrate litep2p into Polkadot SDK (#2944)

[litep2p](https://github.com/altonen/litep2p) is a libp2p-compatible P2P
networking library. It supports all of the features of `rust-libp2p`
that are currently being utilized by Polkadot SDK.

Compared to `rust-libp2p`, `litep2p` has a quite different architecture
which is why the new `litep2p` network backend is only able to use a
little of the existing code in `sc-network`. The design has been mainly
influenced by how we'd wish to structure our networking-related code in
Polkadot SDK: independent higher-levels protocols directly communicating
with the network over links that support bidirectional backpressure. A
good example would be `NotificationHandle`/`RequestResponseHandle`
abstractions which allow, e.g., `SyncingEngine` to directly communicate
with peers to announce/request blocks.

I've tried running `polkadot --network-backend litep2p` with a few
different peer configurations and there is a noticeable reduction in
networking CPU usage. For high load (`--out-peers 200`), networking CPU
usage goes down from ~110% to ~30% (80 pp) and for normal load
(`--out-peers 40`), the usage goes down from ~55% to ~18% (37 pp).

These should not be taken as final numbers because:

a) there are still some low-hanging optimization fruits, such as
enabling [receive window
auto-tuning](https://github.com/libp2p/rust-yamux/pull/176), integrating
`Peerset` more closely with `litep2p` or improving memory usage of the
WebSocket transport
b) fixing bugs/instabilities that incorrectly cause `litep2p` to do less
work will increase the networking CPU usage
c) verification in a more diverse set of tests/conditions is needed

Nevertheless, these numbers should give an early estimate for CPU usage
of the new networking backend.

This PR consists of three separate changes:
* introduce a generic `PeerId` (wrapper around `Multihash`) so that we
don't have use `NetworkService::PeerId` in every part of the code that
uses a `PeerId`
* introduce `NetworkBackend` trait, implement it for the libp2p network
stack and make Polkadot SDK generic over `NetworkBackend`
  * implement `NetworkBackend` for litep2p

The new library should be considered experimental which is why
`rust-libp2p` will remain as the default option for the time being. This
PR currently depends on the master branch of `litep2p` but I'll cut a
new release for the library once all review comments have been
addresses.

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>
Co-authored-by: Alexandru Vasile <alexandru.vasile@parity.io>

polkadot/node/subsystem-bench/src/lib/approval/helpers.rs

@@ -32,7 +32,7 @@ use polkadot_primitives::{
 use polkadot_primitives_test_helpers::dummy_candidate_receipt_bad_sig;
 use rand::{seq::SliceRandom, SeedableRng};
 use rand_chacha::ChaCha20Rng;
-use sc_network::PeerId;
+use sc_network_types::PeerId;
 use sp_consensus_babe::{
 	digests::{CompatibleDigestItem, PreDigest, SecondaryVRFPreDigest},
 	AllowedSlots, BabeEpochConfiguration, Epoch as BabeEpoch, VrfSignature, VrfTranscript,

polkadot/node/subsystem-bench/src/lib/approval/message_generator.rs

@@ -48,7 +48,7 @@ use rand::{seq::SliceRandom, RngCore, SeedableRng};
 use rand_chacha::ChaCha20Rng;
 use rand_distr::{Distribution, Normal};
 use sc_keystore::LocalKeystore;
-use sc_network::PeerId;
+use sc_network_types::PeerId;
 use sc_service::SpawnTaskHandle;
 use sha1::Digest;
 use sp_application_crypto::AppCrypto;

polkadot/node/subsystem-bench/src/lib/approval/test_message.rs

@@ -22,7 +22,7 @@ use itertools::Itertools;
 use parity_scale_codec::{Decode, Encode};
 use polkadot_node_network_protocol::v3 as protocol_v3;
 use polkadot_primitives::{CandidateIndex, Hash, ValidatorIndex};
-use sc_network::PeerId;
+use sc_network_types::PeerId;
 use std::collections::{HashMap, HashSet};
 
 #[derive(Debug, Clone, Encode, Decode, PartialEq, Eq)]

polkadot/node/subsystem-bench/src/lib/availability/mod.rs

@@ -51,8 +51,9 @@ use polkadot_node_subsystem_types::{
 	Span,
 };
 use polkadot_overseer::{metrics::Metrics as OverseerMetrics, Handle as OverseerHandle};
-use polkadot_primitives::GroupIndex;
+use polkadot_primitives::{Block, GroupIndex, Hash};
 use sc_network::request_responses::{IncomingRequest as RawIncomingRequest, ProtocolConfig};
+
 use sc_service::SpawnTaskHandle;
 use serde::{Deserialize, Serialize};
 use std::{ops::Sub, sync::Arc, time::Instant};
@@ -140,20 +141,32 @@ pub fn prepare_test(
 	mode: TestDataAvailability,
 	with_prometheus_endpoint: bool,
 ) -> (TestEnvironment, Vec<ProtocolConfig>) {
-	let (collation_req_receiver, collation_req_cfg) =
-		IncomingRequest::get_config_receiver(&ReqProtocolNames::new(GENESIS_HASH, None));
-	let (pov_req_receiver, pov_req_cfg) =
-		IncomingRequest::get_config_receiver(&ReqProtocolNames::new(GENESIS_HASH, None));
-	let (chunk_req_receiver, chunk_req_cfg) =
-		IncomingRequest::get_config_receiver(&ReqProtocolNames::new(GENESIS_HASH, None));
-	let req_cfgs = vec![collation_req_cfg, pov_req_cfg];
-
 	let dependencies = TestEnvironmentDependencies::default();
 	let availability_state = NetworkAvailabilityState {
 		candidate_hashes: state.candidate_hashes.clone(),
 		available_data: state.available_data.clone(),
 		chunks: state.chunks.clone(),
 	};
+
+	let mut req_cfgs = Vec::new();
+
+	let (collation_req_receiver, collation_req_cfg) = IncomingRequest::get_config_receiver::<
+		Block,
+		sc_network::NetworkWorker<Block, Hash>,
+	>(&ReqProtocolNames::new(GENESIS_HASH, None));
+	req_cfgs.push(collation_req_cfg);
+
+	let (pov_req_receiver, pov_req_cfg) = IncomingRequest::get_config_receiver::<
+		Block,
+		sc_network::NetworkWorker<Block, Hash>,
+	>(&ReqProtocolNames::new(GENESIS_HASH, None));
+
+	let (chunk_req_receiver, chunk_req_cfg) = IncomingRequest::get_config_receiver::<
+		Block,
+		sc_network::NetworkWorker<Block, Hash>,
+	>(&ReqProtocolNames::new(GENESIS_HASH, None));
+	req_cfgs.push(pov_req_cfg);
+
 	let (network, network_interface, network_receiver) = new_network(
 		&state.config,
 		&dependencies,

polkadot/node/subsystem-bench/src/lib/configuration.rs

@@ -21,7 +21,7 @@ use itertools::Itertools;
 use polkadot_primitives::{AssignmentId, AuthorityDiscoveryId, ValidatorId};
 use rand::thread_rng;
 use rand_distr::{Distribution, Normal, Uniform};
-use sc_network::PeerId;
+use sc_network_types::PeerId;
 use serde::{Deserialize, Serialize};
 use sp_consensus_babe::AuthorityId;
 use std::collections::HashMap;

polkadot/node/subsystem-bench/src/lib/network.rs

@@ -67,8 +67,9 @@ use prometheus_endpoint::U64;
 use rand::{seq::SliceRandom, thread_rng};
 use sc_network::{
 	request_responses::{IncomingRequest, OutgoingResponse},
-	PeerId, RequestFailure,
+	RequestFailure,
 };
+use sc_network_types::PeerId;
 use sc_service::SpawnTaskHandle;
 use std::{
 	collections::HashMap,