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>

Cargo.toml

@@ -156,7 +156,7 @@ superstruct = "0.6"
 syn = "1"
 sysinfo = "0.26"
 tempfile = "3"
-tokio = { version = "1", features = ["rt-multi-thread", "sync"] }
+tokio = { version = "1", features = ["rt-multi-thread", "sync", "signal"] }
 tokio-stream = { version = "0.1", features = ["sync"] }
 tokio-util = { version = "0.6", features = ["codec", "compat", "time"] }
 tree_hash = "0.5"