Pool SeekableInputStreams in ParquetFileReader

If https://issues.apache.org/jira/browse/PARQUET-1982 goes through, then we could allow parallel reading of row groups with a pool of SeekableInputStreams. This would significantly boost performance for applications that read data at random positions from a large file.

I've already developed a patch that would enable this functionality. I will link the merge request in the next few days.

Is there a related ticket that i have overlooked?

**Reporter**: [Felix Schmalzel](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=fschmalzel) / @fschmalzel

_{**Note**: *This issue was originally created as [PARQUET-1983](https://issues.apache.org/jira/browse/PARQUET-1983). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Inizia esaminando PARQUET-1982 e l’implementazione esistente di ParquetFileReader per comprendere il prerequisito e la gestione attuale degli stream. Il lavoro è completato quando vengono abilitate le letture parallele dei gruppi di righe tramite un pool di SeekableInputStreams, con il comportamento delle prestazioni convalidato per le letture in posizioni casuali.

Scritto dal modello di indicizzazione a partire dal testo della issue.