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/derived_key.rs

@@ -35,6 +35,11 @@ pub const MOD_R_L: usize = 48;
 #[zeroize(drop)]
 pub struct DerivedKey(ZeroizeHash);
 
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    EmptySeed,
+}
+
 impl DerivedKey {
     /// Instantiates `Self` from some secret seed bytes.
     ///
@@ -42,10 +47,10 @@ impl DerivedKey {
     ///
     /// ## Errors
     ///
-    /// Returns `Err(())` if `seed.is_empty()`, otherwise always returns `Ok(self)`.
-    pub fn from_seed(seed: &[u8]) -> Result<Self, ()> {
+    /// Returns `Err(Error::EmptySeed)` if `seed.is_empty()`, otherwise always returns `Ok(self)`.
+    pub fn from_seed(seed: &[u8]) -> Result<Self, Error> {
         if seed.is_empty() {
-            Err(())
+            Err(Error::EmptySeed)
         } else {
             Ok(Self(derive_master_sk(seed)))
         }

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;