Upgrade to tokio 0.3 (#1839)

## Description

This PR updates Lighthouse to tokio 0.3. It includes a number of dependency updates and some structural changes as to how we create and spawn tasks.

This also brings with it a number of various improvements:

- Discv5 update
- Libp2p update
- Fix for recompilation issues
- Improved UPnP port mapping handling
- Futures dependency update
- Log downgrade to traces for rejecting peers when we've reached our max



Co-authored-by: blacktemplar <blacktemplar@a1.net>

validator_client/src/attestation_service.rs

@@ -5,13 +5,14 @@ use crate::{
 };
 use environment::RuntimeContext;
 use eth2::BeaconNodeHttpClient;
+use futures::future::FutureExt;
 use futures::StreamExt;
 use slog::{crit, error, info, trace};
 use slot_clock::SlotClock;
 use std::collections::HashMap;
 use std::ops::Deref;
 use std::sync::Arc;
-use tokio::time::{delay_until, interval_at, Duration, Instant};
+use tokio::time::{interval_at, sleep_until, Duration, Instant};
 use tree_hash::TreeHash;
 use types::{
     AggregateSignature, Attestation, AttestationData, BitList, ChainSpec, CommitteeIndex, EthSpec,
@@ -211,13 +212,16 @@ impl<T: SlotClock + 'static, E: EthSpec> AttestationService<T, E> {
             .into_iter()
             .for_each(|(committee_index, validator_duties)| {
                 // Spawn a separate task for each attestation.
-                self.inner.context.executor.runtime_handle().spawn(
-                    self.clone().publish_attestations_and_aggregates(
-                        slot,
-                        committee_index,
-                        validator_duties,
-                        aggregate_production_instant,
-                    ),
+                self.inner.context.executor.spawn(
+                    self.clone()
+                        .publish_attestations_and_aggregates(
+                            slot,
+                            committee_index,
+                            validator_duties,
+                            aggregate_production_instant,
+                        )
+                        .map(|_| ()),
+                    "attestation publish",
                 );
             });
 
@@ -278,7 +282,7 @@ impl<T: SlotClock + 'static, E: EthSpec> AttestationService<T, E> {
             // of the way though the slot). As verified in the
             // `delay_triggers_when_in_the_past` test, this code will still run
             // even if the instant has already elapsed.
-            delay_until(aggregate_production_instant).await;
+            sleep_until(aggregate_production_instant).await;
 
             // Start the metrics timer *after* we've done the delay.
             let _aggregates_timer = metrics::start_timer_vec(
@@ -552,7 +556,7 @@ mod tests {
     use futures::future::FutureExt;
     use parking_lot::RwLock;
 
-    /// This test is to ensure that a `tokio_timer::Delay` with an instant in the past will still
+    /// This test is to ensure that a `tokio_timer::Sleep` with an instant in the past will still
     /// trigger.
     #[tokio::test]
     async fn delay_triggers_when_in_the_past() {
@@ -560,7 +564,7 @@ mod tests {
         let state_1 = Arc::new(RwLock::new(in_the_past));
         let state_2 = state_1.clone();
 
-        delay_until(in_the_past)
+        sleep_until(in_the_past)
             .map(move |()| *state_1.write() = Instant::now())
             .await;