Upgrade to tokio 0.3 (#1839)

## Description

This PR updates Lighthouse to tokio 0.3. It includes a number of dependency updates and some structural changes as to how we create and spawn tasks.

This also brings with it a number of various improvements:

- Discv5 update
- Libp2p update
- Fix for recompilation issues
- Improved UPnP port mapping handling
- Futures dependency update
- Log downgrade to traces for rejecting peers when we've reached our max



Co-authored-by: blacktemplar <blacktemplar@a1.net>

testing/node_test_rig/Cargo.toml

@@ -13,7 +13,7 @@ tempdir = "0.3.7"
 reqwest = { version = "0.10.8", features = ["native-tls-vendored"] }
 url = "2.1.1"
 serde = "1.0.116"
-futures = "0.3.5"
+futures = "0.3.7"
 genesis = { path = "../../beacon_node/genesis" }
 eth2 = { path = "../../common/eth2" }
 validator_client = { path = "../../validator_client" }

testing/node_test_rig/src/lib.rs

@@ -86,6 +86,7 @@ pub fn testing_client_config() -> ClientConfig {
     // Setting ports to `0` means that the OS will choose some available port.
     client_config.network.libp2p_port = 0;
     client_config.network.discovery_port = 0;
+    client_config.network.upnp_enabled = false;
     client_config.http_api.enabled = true;
     client_config.http_api.listen_port = 0;
     client_config.websocket_server.enabled = true;