OTAP Exporter remove sleeps from unit tests

[albertlockett]

The OTAP exporter uses some random sleeps while the server is starting/stopping to test the behaviour of sending gRPC requests while the server is not ready tor receive connections.

otel-arrow/rust/otap-dataflow/crates/otap/src/otap_exporter.rs

Lines 846 to 854 in 785f92e

	// send a request before while the server isn't running and check how we handle it
	let log_message = create_otap_batch(LOG_BATCH_ID, ArrowPayloadType::Logs);
	pdata_tx
	.send(OtapPdata::new_default(log_message.into()))
	.await
	.expect("Failed to send log message");
	// TODO instead of sleeping here, once we handle ACK/NACK we should wait to get a NACK
	// from the control channel
	tokio::time::sleep(Duration::from_millis(5)).await;

However, this is fragile and actually seems to not work in windows:
https://github.com/open-telemetry/otel-arrow/actions/runs/20154182152/job/57898503464?pr=1594

We could update the test to wait to receive ACK or NACK before proceeding instead of relying on random sleeps. This would probably make the test more reliable.