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/beacon_chain/src/lib.rs

@@ -1,4 +1,3 @@
-#![recursion_limit = "128"] // For lazy-static
 pub mod attestation_rewards;
 pub mod attestation_verification;
 mod attester_cache;