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>

consensus/fork_choice/tests/tests.rs

@@ -635,12 +635,7 @@ fn invalid_block_future_slot() {
             |block, _| {
                 block.slot = block.slot + 1;
             },
-            |err| {
-                assert_invalid_block!(
-                    err,
-                    InvalidBlock::FutureSlot { .. }
-                )
-            },
+            |err| assert_invalid_block!(err, InvalidBlock::FutureSlot { .. }),
         );
 }
 

consensus/int_to_bytes/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 edition = "2018"
 
 [dependencies]
-bytes = "0.6.0"
+bytes = "1.0.1"
 
 [dev-dependencies]
 yaml-rust = "0.4.4"

consensus/types/src/eth_spec.rs

@@ -56,7 +56,7 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
     /*
      * Misc
      */
-    type MaxValidatorsPerCommittee: Unsigned + Clone + Sync + Send + Debug + PartialEq + Eq;
+    type MaxValidatorsPerCommittee: Unsigned + Clone + Sync + Send + Debug + PartialEq + Eq + Unpin;
     /*
      * Time parameters
      */