Appease Clippy 1.68 and refactor http_api (#4068)

## Proposed Changes

Two tiny updates to satisfy Clippy 1.68

Plus refactoring of the `http_api` into less complex types so the compiler can chew and digest them more easily.

Co-authored-by: Michael Sproul <michael@sigmaprime.io>

beacon_node/http_api/tests/main.rs

@@ -1,5 +1,4 @@
 #![cfg(not(debug_assertions))] // Tests are too slow in debug.
-#![recursion_limit = "256"]
 
 pub mod common;
 pub mod fork_tests;