[C++][Gandiva] Add DumpIR to Filter/Projector classes

[asfimport]

The tool should take a protobuf expression from stdin and dump the IR to stdout. This might require some though as the schema is not always known. It could mean a refactor to support plain array, especially for the Filter kernel.

Reporter: Francois Saint-Jacques / @fsaintjacques
Assignee: Francois Saint-Jacques / @fsaintjacques

PRs and other links:

• GitHub Pull Request #6417

_{Note: This issue was originally created as ARROW-7819. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 6417
#6417