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>

beacon_node/execution_layer/src/test_utils/mod.rs

@@ -25,7 +25,7 @@ use warp::{http::StatusCode, Filter, Rejection};
 use crate::EngineCapabilities;
 pub use execution_block_generator::{generate_pow_block, Block, ExecutionBlockGenerator};
 pub use hook::Hook;
-pub use mock_builder::{Context as MockBuilderContext, MockBuilder, MockBuilderServer, Operation};
+pub use mock_builder::{MockBuilder, Operation};
 pub use mock_execution_layer::MockExecutionLayer;
 
 pub const DEFAULT_TERMINAL_DIFFICULTY: u64 = 6400;