Suggestion: enable `unreachable_pub` lint at workspace level

Why looking at the code I thought I could use `InProgressSpillFile` since it marked as `pub`, or the function `create_in_progress_file` that is also `pub`, but `InProgressSpillFile` mod is behind `pub(crate)` so to avoid confusion when reading the source code

I want to enable `unreachable_pub` lint at the workspace level so this won't happen since you will be forced to specify the correct visibility

Applying this can be done using: `cargo fix --workspace --all-targets`

Start at the workspace-level Cargo configuration and inspect how lint settings are currently defined. Run `cargo fix --workspace --all-targets`, review the visibility changes it proposes, and verify that the workspace builds and the `unreachable_pub` lint is enabled without remaining warnings.

Written by the indexing model from the issue text.