Add Nethermind integration tests (#3100)

## Proposed Changes

Extend the current Geth merge integration tests to support Nethermind.

testing/execution_engine_integration/src/main.rs

@@ -3,26 +3,37 @@
 /// It will first attempt to build any supported integration clients, then it will run tests.
 ///
 /// A return code of `0` indicates the tests succeeded.
-mod build_geth;
+mod build_utils;
 mod execution_engine;
 mod genesis_json;
+mod geth;
+mod nethermind;
 mod test_rig;
 
-use execution_engine::Geth;
+use geth::GethEngine;
+use nethermind::NethermindEngine;
 use test_rig::TestRig;
 
 /// Set to `false` to send logs to the console during tests. Logs are useful when debugging.
-const SUPPRESS_LOGS: bool = false;
+const SUPPRESS_LOGS: bool = true;
 
 fn main() {
     if cfg!(windows) {
         panic!("windows is not supported, only linux");
     }
 
-    test_geth()
+    test_geth();
+    test_nethermind();
 }
 
 fn test_geth() {
-    build_geth::build();
-    TestRig::new(Geth).perform_tests_blocking();
+    let test_dir = build_utils::prepare_dir();
+    geth::build(&test_dir);
+    TestRig::new(GethEngine).perform_tests_blocking();
+}
+
+fn test_nethermind() {
+    let test_dir = build_utils::prepare_dir();
+    nethermind::build(&test_dir);
+    TestRig::new(NethermindEngine).perform_tests_blocking();
 }