ProtoReader does not iterate over the parquet file correctly.

The `ProtoParquetReader` does not iterate over the parquet file correctly, but it gets stuck in the first element and keeps reading as many times as elements the file contained.

In my Scala example I am just reading from a local file that I know for sure it contains right data.

```

val hadoopCOnf = new Configuration()

val outfile: String = genTemporaryFile()

val r: ParquetReader[Event.Builder] = {
ProtoParquetReader.builder[Event.Builder](new Path(outfile)).withConf(hadoopCOnf).build()
}

```

Notice that the proto schema that I am using is generated from 

The generated proto implements com.google.protobuf.GeneratedMessageV3.

See an example on how the ProtoParquetReader is created line(65 and 69): 

and here how it is used (notice that is defined for only one record, the same one for multiple records would fail) 

**Reporter**: [Pau Alarcon ](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=paualarco)

_{**Note**: *This issue was originally created as [PARQUET-1871](https://issues.apache.org/jira/browse/PARQUET-1871). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Beginne mit ProtoParquetReader und vergleiche seine Erstellung in monix-connects ProtoParquetFixture.scala um die Zeilen 65–69 mit seiner Verwendung in ProtoParquetSpec.scala um Zeile 83. Reproduziere das Verhalten mit mehreren Datensätzen und überprüfe, dass die Iteration aufeinanderfolgende Datensätze zurückgibt, anstatt den ersten zu wiederholen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.