Add a feature to make encryption optional

[corwinjoy]

Is your feature request related to a problem or challenge?

In the recent PR to add modular encryption (#16351) it was suggested that a feature should be added to make encryption optional. This is a good feature to have since it can help minimize crate dependencies and code bloat.

Describe the solution you'd like

See followup PR to address this.

Describe alternatives you've considered

No response

Additional context

No response

[Vyquos]

thanks for implementing this! I'm trying to get datafusion (with parquet) running on the hermit unikernel, and not having to support unnecessary crypto primitives is a tremendous advantage.
Unfortunately, while #16649 technically makes the encryption feature of parquet optional, the feature is still enabled in the workspace root Cargo.toml. I'm not very familiar with the datafusion repo, but for this simple change, I will try creating a PR.

[Jefffrey]

Looks like #17700 has disabled it from workspace root so this is good to close