fix: modify perf_producer to run properly (#318)

### Motivation
I noticed the `perf_producer` is not working properly as follows. I want to fix it.

```
% node perf/perf_producer.js -u pulsar://localhost:6650 -t persistent://public/default/my-topic -i 1000
----------------------
size: 1024
url: pulsar://localhost:6650
topic: persistent://public/default/my-topic
iteration: 1000
messages: 1000
----------------------
/Users/equanz/src/pulsar-client-node/perf/perf_producer.js:107
      histogram.getMean(),
                ^

TypeError: histogram.getMean is not a function
    at /Users/equanz/src/pulsar-client-node/perf/perf_producer.js:107:17

Node.js v18.6.0
```

### Modifications

* Modify the `perf_producer` to address [migration procedures](https://github.com/HdrHistogram/HdrHistogramJS/tree/v2.0.1#migrating-from-v1-to-v2)

perf/perf_producer.js

diff --git a/perf/perf_producer.js b/perf/perf_producer.js
index fbe12f1..4638b59 100644
--- a/perf/perf_producer.js
+++ b/perf/perf_producer.js
@@ -77,7 +77,7 @@
   const numOfMessages = commander.messages;
   for (let i = 0; i < commander.iteration; i += 1) {
     const histogram = hdr.build({
-      bitBucketSize: 0,
+      bitBucketSize: 64,
       highestTrackableValue: 120000 * 1000,
       numberOfSignificantValueDigits: 5,
     });
@@ -104,7 +104,7 @@
     console.log('Throughput produced: %f  msg/s --- %f Mbit/s --- Latency: mean: %f ms - med: %f - 95pct: %f - 99pct: %f - 99.9pct: %f - 99.99pct: %f - Max: %f',
       rate.toFixed(3),
       throuhputMbit.toFixed(3),
-      histogram.getMean(),
+      histogram.mean,
       histogram.getValueAtPercentile(50),
       histogram.getValueAtPercentile(95),
       histogram.getValueAtPercentile(99),