Error log to verbose in AbstractParallelEoSStreamProcessor

Hi,

Context is pretty big and lead to an enormous log for [this code](https://github.com/confluentinc/parallel-consumer/blob/d337fe5dc1f1669293d2a29f12610ba2d6fbaab4/parallel-consumer-core/src/main/java/io/confluent/parallelconsumer/internal/AbstractParallelEoSStreamProcessor.java#L1280) which will be truncated in some tooling:

```java
String msg = msg("Exception caught in user function running stage, registering WC as failed, returning to" +
" mailbox. Context: {}", context, e);
if (cause instanceof PCRetriableException) {
log.debug("Explicit " + PCRetriableException.class.getSimpleName() + " caught, logging at DEBUG only. " + msg, e);
} else {
log.error(msg, e);
}
```

I would be nice to have a
smaller toString for the context

Regards
Benoit