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>

testing/remote_signer_test/src/api_test_signer.rs

@@ -26,10 +26,7 @@ impl ApiTestSigner<E> {
 
         let client = environment
             .runtime()
-            .block_on(tokio_compat_02::FutureExt::compat(Client::new(
-                runtime_context,
-                &matches,
-            )))
+            .block_on(Client::new(runtime_context, &matches))
             .map_err(|e| format!("Failed to init Rest API: {}", e))
             .unwrap();
 

testing/remote_signer_test/src/consumer.rs

@@ -30,13 +30,13 @@ pub fn do_sign_request<E: EthSpec, T: RemoteSignerObject>(
 ) -> Result<String, Error> {
     let runtime = Builder::new_multi_thread().enable_all().build().unwrap();
 
-    runtime.block_on(tokio_compat_02::FutureExt::compat(test_client.sign(
+    runtime.block_on(test_client.sign(
         &test_input.public_key,
         test_input.bls_domain,
         test_input.data,
         test_input.fork,
         test_input.genesis_validators_root,
-    )))
+    ))
 }
 
 #[derive(Serialize)]