[Java][Gandiva] Expose Dremio build and tests as new optional container/test

Dremio uses Arrow Java and Gandiva extensively and could provide additional test coverage for the project. We should find a way to expose the downstream build of Dremio as an optional build so major changes can better be evaluated against downstream effects.

@praveenbingo, assigning to you for now but let's figure out who at Dremio can pick this up.

**Reporter**: [Jacques Nadeau](https://issues.apache.org/jira/browse/ARROW-3887) / @jacques-n

_{**Note**: *This issue was originally created as [ARROW-3887](https://issues.apache.org/jira/browse/ARROW-3887). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the Arrow Java and Gandiva build configuration and the existing optional container or test mechanisms. Investigate how Dremio's downstream build could be exposed as an optional build, and define completion as an optional Dremio build and test path that evaluates downstream effects.

Written by the indexing model from the issue text.