[Java] reduce heap footprint of ValueVectors

In some scenarios, we hold lots of value vectors in memory eg. during join, aggregation. The heap analysis shows that the costs are as follows for a simple IntVector (used VisualVM on mac) :

IntVector : 80 bytes

vector.types.pojo.FieldType : 41 bytes

vector.types.pojo.Field : 40 bytes

IntReaderImpl : 28 bytes

I'll use this Jira to track ways to reduce the heap usage.

**Reporter**: [Pindikura Ravindra](https://issues.apache.org/jira/browse/ARROW-5482) / @pravindra
#### Related issues:
- [[Java] remove FieldReader from ValueVector](https://github.com/apache/arrow-java/issues/411) (is a parent of)
- [[Java] add ValueVector constructors that take a Field object](https://github.com/apache/arrow/issues/21932) (is a parent of)

_{**Note**: *This issue was originally created as [ARROW-5482](https://issues.apache.org/jira/browse/ARROW-5482). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Empieza leyendo las implementaciones de Java ValueVector y el issue relacionado “remove FieldReader from ValueVector” (#411); después, reproduce con VisualVM el perfil de heap de IntVector indicado. Se considerará terminado cuando se haya medido una reducción de los costes de memoria de ValueVector reportados y se hayan documentado los escenarios afectados y las compensaciones.

Escrito por el modelo de indexación a partir del texto del issue.