Integrate tracing (#6339)

Tracing Integration
- [reference](5bbf1859e9/projects/project-ideas.md (L297))


  - [x] replace slog & log with tracing throughout the codebase
- [x] implement custom crit log
- [x] make relevant changes in the formatter
- [x] replace sloggers
- [x] re-write SSE logging components

cc: @macladson @eserilev

beacon_node/tests/test.rs

@@ -25,8 +25,6 @@ fn build_node<E: EthSpec>(env: &mut Environment<E>) -> LocalBeaconNode<E> {
 #[test]
 fn http_server_genesis_state() {
     let mut env = env_builder()
-        .test_logger()
-        .expect("should build env logger")
         .multi_threaded_tokio_runtime()
         .expect("should start tokio runtime")
         .build()