[CELEBORN-1640] NettyMemoryMetrics supports numHeapArenas, numDirectA…

…renas, tinyCacheSize, smallCacheSize, normalCacheSize, numThreadLocalCaches and chunkSize

### What changes were proposed in this pull request?

`NettyMemoryMetrics` supports `numHeapArenas`, `numDirectArenas`, `tinyCacheSize`, `smallCacheSize`, `normalCacheSize`, `numThreadLocalCaches` and `chunkSize` from `PooledByteBufAllocatorMetric`. Meanwhile, remove `server_` prefix from metric name of netty memory metric in `monitoring.md`.

### Why are the changes needed?

`PooledByteBufAllocatorMetric` provides the following API to support netty memory metrics:

```
public int numHeapArenas() {
  return this.allocator.numHeapArenas();
}

public int numDirectArenas() {
  return this.allocator.numDirectArenas();
}

public List<PoolArenaMetric> heapArenas() {
  return this.allocator.heapArenas();
}

public List<PoolArenaMetric> directArenas() {
  return this.allocator.directArenas();
}

public int numThreadLocalCaches() {
  return this.allocator.numThreadLocalCaches();
}

public int tinyCacheSize() {
  return this.allocator.tinyCacheSize();
}

public int smallCacheSize() {
  return this.allocator.smallCacheSize();
}

public int normalCacheSize() {
  return this.allocator.normalCacheSize();
}

public int chunkSize() {
  return this.allocator.chunkSize();
}

public long usedHeapMemory() {
  return this.allocator.usedHeapMemory();
}

public long usedDirectMemory() {
  return this.allocator.usedDirectMemory();
}
```

`NettyMemoryMetrics` only supports `usedHeapMemory` and `usedDirectMemory`, which could support `numHeapArenas`, `numDirectArenas`, `tinyCacheSize`, `smallCacheSize`, `normalCacheSize`, `numThreadLocalCaches` and `chunkSize` from `PooledByteBufAllocatorMetric`.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

[Celeborn Grafana Dashboard](https://stenicholas.grafana.net/public-dashboards/a520ca36a33843a38bbde28387023f97)

Closes apache#2802 from SteNicholas/CELEBORN-1640.

Authored-by: SteNicholas <[email protected]>
Signed-off-by: mingji <[email protected]>