Set up Comet + Iceberg integration tests in CI

[andygrove]

What is the problem the feature request solves?

We want to avoid making code changes in Comet that cause regressions with the Iceberg integration.

I would like to add an integration test that we can run as a GitHub workflow.

The steps would be:

• Clone a specific version or revision of Iceberg
• Apply a diff for the changes documented in https://github.com/apache/datafusion-comet/pull/1683
• Run the integration test to run queries against Iceberg with and without Comet and ensure that the results match

Describe the potential solution

No response

Additional context

No response

[hsiang-c]

take