[Java] Avro - Experiment with "compiled" consumer delegates for performance.

All consumers that rely on delegates (e.g. struct, composite, list, union, ...) require  megamorphic lookups which can't be inlined well by JIT.  

We should verify the performance different of a hand-coded consumer vs an existing delegate consumer

i.e. something like:

void consume(Decoder d) {

  ((IntConsumer)delegate).consume(d);

}

compared to the existing implementation.  It is expected we will see a decent amount of performance improvement from this approach.  If we do, we should add an option to converter to generate new custom classes on the fly, that mimic the hand-coded option.

**Reporter**: [Micah Kornfield](https://issues.apache.org/jira/browse/ARROW-6595) / @emkornfield

_{**Note**: *This issue was originally created as [ARROW-6595](https://issues.apache.org/jira/browse/ARROW-6595). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Comece localizando os consumers baseados em delegate e o caminho do consumer implementado manualmente descritos na issue. Compare o desempenho deles e, em seguida, avalie se classes personalizadas geradas por um converter são justificadas; considera-se concluído quando houver uma comparação documentada e uma decisão de implementação com escopo definido.

Escrita pelo modelo de indexação a partir do texto da issue.