Update to tokio 1.1 (#2172)

## Issue Addressed

resolves #2129
resolves #2099 
addresses some of #1712
unblocks #2076
unblocks #2153 

## Proposed Changes

- Updates all the dependencies mentioned in #2129, except for web3. They haven't merged their tokio 1.0 update because they are waiting on some dependencies of their own. Since we only use web3 in tests, I think updating it in a separate issue is fine. If they are able to merge soon though, I can update in this PR. 

- Updates `tokio_util` to 0.6.2 and `bytes` to 1.0.1.

- We haven't made a discv5 release since merging tokio 1.0 updates so I'm using a commit rather than release atm. **Edit:** I think we should merge an update of `tokio_util` to 0.6.2 into discv5 before this release because it has panic fixes in `DelayQueue`  --> PR in discv5:  https://github.com/sigp/discv5/pull/58

## Additional Info

tokio 1.0 changes that required some changes in lighthouse:

- `interval.next().await.is_some()` -> `interval.tick().await`
- `sleep` future is now `!Unpin` -> https://github.com/tokio-rs/tokio/issues/3028
- `try_recv` has been temporarily removed from `mpsc` -> https://github.com/tokio-rs/tokio/issues/3350
- stream features have moved to `tokio-stream` and `broadcast::Receiver::into_stream()` has been temporarily removed -> `https://github.com/tokio-rs/tokio/issues/2870
- I've copied over the `BroadcastStream` wrapper from this PR, but can update to use `tokio-stream` once it's merged https://github.com/tokio-rs/tokio/pull/3384

Co-authored-by: realbigsean <seananderson33@gmail.com>

common/task_executor/Cargo.toml

@@ -5,10 +5,9 @@ authors = ["Sigma Prime <contact@sigmaprime.io>"]
 edition = "2018"
 
 [dependencies]
-tokio = { version = "0.3.2", features = ["rt"] }
+tokio = { version = "1.1.0", features = ["rt"] }
 slog = "2.5.2"
 futures = "0.3.7"
 exit-future = "0.2.0"
 lazy_static = "1.4.0"
 lighthouse_metrics = { path = "../lighthouse_metrics" }
-tokio-compat-02 = "0.1"

common/task_executor/src/lib.rs

@@ -5,7 +5,6 @@ use futures::prelude::*;
 use slog::{debug, o, trace};
 use std::sync::Weak;
 use tokio::runtime::Runtime;
-use tokio_compat_02::FutureExt;
 
 /// A wrapper over a runtime handle which can spawn async and blocking tasks.
 #[derive(Clone)]
@@ -63,7 +62,7 @@ impl TaskExecutor {
         if let Some(int_gauge) = metrics::get_int_gauge(&metrics::ASYNC_TASKS_COUNT, &[name]) {
             // Task is shutdown before it completes if `exit` receives
             let int_gauge_1 = int_gauge.clone();
-            let future = future::select(Box::pin(task.compat()), exit).then(move |either| {
+            let future = future::select(Box::pin(task), exit).then(move |either| {
                 match either {
                     future::Either::Left(_) => trace!(log, "Async task completed"; "task" => name),
                     future::Either::Right(_) => {
@@ -99,12 +98,10 @@ impl TaskExecutor {
     ) {
         if let Some(int_gauge) = metrics::get_int_gauge(&metrics::ASYNC_TASKS_COUNT, &[name]) {
             let int_gauge_1 = int_gauge.clone();
-            let future = task
-                .then(move |_| {
-                    int_gauge_1.dec();
-                    futures::future::ready(())
-                })
-                .compat();
+            let future = task.then(move |_| {
+                int_gauge_1.dec();
+                futures::future::ready(())
+            });
 
             int_gauge.inc();
             if let Some(runtime) = self.runtime.upgrade() {
@@ -186,7 +183,7 @@ impl TaskExecutor {
 
             int_gauge.inc();
             if let Some(runtime) = self.runtime.upgrade() {
-                Some(runtime.spawn(future.compat()))
+                Some(runtime.spawn(future))
             } else {
                 debug!(self.log, "Couldn't spawn task. Runtime shutting down");
                 None