Add bones for handling RPC methods on test server

beacon_node/execution_layer/src/test_utils/handle_rpc.rs

@@ -0,0 +1,10 @@
+use super::Context;
+use std::sync::Arc;
+use types::EthSpec;
+
+pub async fn handle_rpc<T: EthSpec>(
+    body: serde_json::Value,
+    ctx: Arc<Context<T>>,
+) -> Result<serde_json::Value, String> {
+    todo!("handle_rpc")
+}