Bookie GC pressure when use ReadEntryProcessorV3

**BUG REPORT**
When we get entry from bookie in ReadEntryProcessorV3#readEntry, the response is DirectByteBuf, the v3 use proto buf response. So it will copy byte array to proto buf builder, it will use heap memory.

If the user read request is frequent, it will introduce gc pressure.

https://github.com/apache/bookkeeper/blob/ca7d7c23e3aa572befeb447157b3ef9d96bb1449/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/ReadEntryProcessorV3.java#L179

```
public static ByteString copyFrom(ByteBuffer bytes, int size) {
checkRange(0, size, bytes.remaining());
byte[] copy = new byte[size];
bytes.get(copy);
return new LiteralByteString(copy);
}
```