Clippy 1.49.0 updates and dht persistence test fix (#2156)

## Issue Addressed

`test_dht_persistence` failing

## Proposed Changes

Bind `NetworkService::start` to an underscore prefixed variable rather than `_`.  `_` was causing it to be dropped immediately

This was failing 5/100 times before this update, but I haven't been able to get it to fail after updating it

Co-authored-by: realbigsean <seananderson33@gmail.com>

crypto/eth2_key_derivation/src/lib.rs

@@ -8,4 +8,5 @@ mod secret_bytes;
 
 pub use bls::ZeroizeHash;
 pub use derived_key::DerivedKey;
+pub use derived_key::Error as DerivedKeyError;
 pub use plain_text::PlainText;