Add test that drops the node in an async context

.. as tokio tends to panic if dropping a runtime in an async context and
we're not super careful. Here, we add some test coverage for this edge
case in Rust tests.

Author: tnull

tests/integration_tests_rust.rs

@@ -1457,3 +1457,14 @@ fn spontaneous_send_with_custom_preimage() {
 		panic!("Expected receiver to have spontaneous PaymentKind with preimage");
 	}
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+async fn drop_in_async_context() {
+	let (_bitcoind, electrsd) = setup_bitcoind_and_electrsd();
+	let chain_source = TestChainSource::Esplora(&electrsd);
+	let seed_bytes = vec![42u8; 64];
+
+	let config = random_config(true);
+	let node = setup_node(&chain_source, config, Some(seed_bytes));
+	node.stop().unwrap();
+}