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/rpc/handler.rs

@@ -7,6 +7,7 @@ use super::{RPCReceived, RPCSend};
 use crate::rpc::protocol::{InboundFramed, OutboundFramed};
 use fnv::FnvHashMap;
 use futures::prelude::*;
+use futures::{Sink, SinkExt};
 use libp2p::core::upgrade::{
     InboundUpgrade, NegotiationError, OutboundUpgrade, ProtocolError, UpgradeError,
 };
@@ -133,7 +134,7 @@ enum HandlerState {
     ///
     /// While in this state the handler rejects new requests but tries to finish existing ones.
     /// Once the timer expires, all messages are killed.
-    ShuttingDown(Sleep),
+    ShuttingDown(Box<Sleep>),
     /// The handler is deactivated. A goodbye has been sent and no more messages are sent or
     /// received.
     Deactivated,
@@ -239,9 +240,9 @@ where
                 self.dial_queue.push((id, req));
             }
 
-            self.state = HandlerState::ShuttingDown(sleep_until(
+            self.state = HandlerState::ShuttingDown(Box::new(sleep_until(
                 TInstant::now() + Duration::from_secs(SHUTDOWN_TIMEOUT_SECS as u64),
-            ));
+            )));
         }
     }