When you implement an ingest factory which implements `Closeable`:

```java
public static final class Factory extends AbstractProcessorFactory<MyProcessor> implements Closeable {
    @OverRide
    public void close() throws IOException {
        logger.debug("closing my processor factory");
    }
}
```

The `close()` method is never called which could lead to some leak threads when we close a node.

The `ProcessorsRegistry#close()` method exists though and seems to do the right job:

```java
@OverRide
public void close() throws IOException {
    List<Closeable> closeables = new ArrayList<>();
    for (Processor.Factory factory : processorFactories.values()) {
        if (factory instanceof Closeable) {
            closeables.add((Closeable) factory);
        }
    }
    IOUtils.close(closeables);
}
```

But apparently this method is never called in `Node#stop()`.

Closes elastic#17625.