Improve tokio task execution (#1181)

* Add logging on shutdown

* Replace tokio::spawn with handle.spawn

* Upgrade tokio

* Add a task executor

* Beacon chain tasks use task executor

* Validator client tasks use task executor

* Rename runtime_handle to executor

* Add duration histograms; minor fixes

* Cleanup

* Fix logs

* Fix tests

* Remove random file

* Get enr dependency instead of libp2p

* Address some review comments

* Libp2p takes a TaskExecutor

* Ugly fix libp2p tests

* Move TaskExecutor to own file

* Upgrade Dockerfile rust version

* Minor fixes

* Revert "Ugly fix libp2p tests"

This reverts commit 58d4bb690f52de28d893943b7504d2d0c6621429.

* Pretty fix libp2p tests

* Add spawn_without_exit; change Counter to Gauge

* Tidy

* Move log from RuntimeContext to TaskExecutor

* Fix errors

* Replace histogram with int_gauge for async tasks

* Fix todo

* Fix memory leak in test by exiting all spawned tasks at the end

lcli/src/eth1_genesis.rs

@@ -46,7 +46,7 @@ pub fn run<T: EthSpec>(mut env: Environment<T>, matches: &ArgMatches<'_>) -> Res
     config.lowest_cached_block_number = eth2_testnet_config.deposit_contract_deploy_block;
     config.follow_distance = spec.eth1_follow_distance / 2;
 
-    let genesis_service = Eth1GenesisService::new(config, env.core_context().log.clone());
+    let genesis_service = Eth1GenesisService::new(config, env.core_context().log().clone());
 
     env.runtime().block_on(async {
         let _ = genesis_service