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/peer_manager/mod.rs

@@ -972,7 +972,7 @@ impl<TSpec: EthSpec> Stream for PeerManager<TSpec> {
 
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         // perform the heartbeat when necessary
-        while let Poll::Ready(Some(_)) = self.heartbeat.poll_next_unpin(cx) {
+        while let Poll::Ready(_) = self.heartbeat.poll_tick(cx) {
             self.heartbeat();
         }
 
@@ -1011,8 +1011,10 @@ impl<TSpec: EthSpec> Stream for PeerManager<TSpec> {
             }
         }
 
-        if !matches!(self.network_globals.sync_state(), SyncState::SyncingFinalized{..}|SyncState::SyncingHead{..})
-        {
+        if !matches!(
+            self.network_globals.sync_state(),
+            SyncState::SyncingFinalized { .. } | SyncState::SyncingHead { .. }
+        ) {
             loop {
                 match self.status_peers.poll_next_unpin(cx) {
                     Poll::Ready(Some(Ok(peer_id))) => {