panic in integration test does not cause it to terminate

[tiziano88]

This took a few hours of debugging to figure out why tests were hanging; it turns out that after calling block_on from an executor, a panic in the main thread does not actually cause the tests to terminate.

To reproduce, add a panic!("x"); after the following code

oak/oak_functions_launcher/benches/integration_benches.rs

Lines 96 to 104 in f417c1b

	let (launched_instance, connector_handle, initialize_response) = runtime
	.block_on(oak_functions_launcher::create(
	params,
	lookup_data_config,
	config.wasm_path.to_path_buf(),
	constant_response_size,
	))
	.expect("Failed to create launcher");
	log::info!("created launcher instance");

and rerun the tests with

cargo test --package=oak_functions_launcher --all-targets bench_ --verbose -- --nocapture

The panic will be logged, but the test will hang, presumably because there are other threads / processes in the background.