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>

beacon_node/eth2_libp2p/src/discovery/enr_ext.rs

@@ -221,8 +221,9 @@ impl CombinedKeyExt for CombinedKey {
     fn from_libp2p(key: &libp2p::core::identity::Keypair) -> Result<CombinedKey, &'static str> {
         match key {
             Keypair::Secp256k1(key) => {
-                let secret = discv5::enr::k256::ecdsa::SigningKey::new(&key.secret().to_bytes())
-                    .expect("libp2p key must be valid");
+                let secret =
+                    discv5::enr::k256::ecdsa::SigningKey::from_bytes(&key.secret().to_bytes())
+                        .expect("libp2p key must be valid");
                 Ok(CombinedKey::Secp256k1(secret))
             }
             Keypair::Ed25519(key) => {
@@ -277,7 +278,7 @@ mod tests {
     fn test_secp256k1_peer_id_conversion() {
         let sk_hex = "df94a73d528434ce2309abb19c16aedb535322797dbd59c157b1e04095900f48";
         let sk_bytes = hex::decode(sk_hex).unwrap();
-        let secret_key = discv5::enr::k256::ecdsa::SigningKey::new(&sk_bytes).unwrap();
+        let secret_key = discv5::enr::k256::ecdsa::SigningKey::from_bytes(&sk_bytes).unwrap();
 
         let libp2p_sk = libp2p::identity::secp256k1::SecretKey::from_bytes(sk_bytes).unwrap();
         let secp256k1_kp: libp2p::identity::secp256k1::Keypair = libp2p_sk.into();

beacon_node/eth2_libp2p/src/discovery/mod.rs

@@ -896,7 +896,7 @@ impl<TSpec: EthSpec> Discovery<TSpec> {
             }
             EventStream::InActive => {} // ignore checking the stream
             EventStream::Present(ref mut stream) => {
-                while let Ok(event) = stream.try_recv() {
+                while let Poll::Ready(Some(event)) = stream.poll_recv(cx) {
                     match event {
                         // We filter out unwanted discv5 events here and only propagate useful results to
                         // the peer manager.