Use only lighthouse types in the mock builder (#4793)

## Proposed Changes

- only use LH types to avoid build issues
- use warp instead of axum for the server to avoid importing the dep

## Additional Info

- wondering if we can move the `execution_layer/test_utils` to its own crate and import it as a dev dependency
- this would be made easier by separating out our engine API types into their own crate so we can use them in the test crate
- or maybe we can look into using reth types for the engine api if they are in their own crate


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

validator_client/src/http_api/tests/keystores.rs

@@ -2146,7 +2146,7 @@ async fn import_remotekey_web3signer_enabled() {
         assert_eq!(tester.vals_total(), 1);
         assert_eq!(tester.vals_enabled(), 1);
         let vals = tester.initialized_validators.read();
-        let web3_vals = vals.validator_definitions().clone();
+        let web3_vals = vals.validator_definitions();
 
         // Import remotekeys.
         let import_res = tester
@@ -2164,7 +2164,7 @@ async fn import_remotekey_web3signer_enabled() {
         assert_eq!(tester.vals_total(), 1);
         assert_eq!(tester.vals_enabled(), 1);
         let vals = tester.initialized_validators.read();
-        let remote_vals = vals.validator_definitions().clone();
+        let remote_vals = vals.validator_definitions();
 
         // Web3signer should not be overwritten since it is enabled.
         assert!(web3_vals == remote_vals);