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/Cargo.toml

@@ -56,7 +56,7 @@ itertools = { workspace = true }
 monitoring_api = { workspace = true }
 sensitive_url = { workspace = true }
 task_executor = { workspace = true }
-reqwest = { workspace = true }
+reqwest = { workspace = true, features = ["native-tls"] }
 url = { workspace = true }
 malloc_utils = { workspace = true }
 sysinfo = { workspace = true }