Enable clippy lint clippy::allow_attributes

Same as we did for datafusion: apache/datafusion#18881

This should not be done in one big PR, but preferably by crates (or chunks of crates) until we can enable it at the workspace level

Also fix this line in doc once this is done:

arrow-rs/CONTRIBUTING.md

Line 195 in a1ec3b1

    
           Search for `allow(clippy::` in the codebase to identify lints that are ignored/allowed. We currently prefer ignoring lints on the lowest unit possible.

I’ll work on enabling this lint for the arrow-string crate.

Enable allow_attributes lint for arrow-string (#10482)

Introduce workspace lints (#10533)

Enable a few more clippy lints (#10558)

I'll work on enabling clippy::allow_attributes for the arrow-arith crate.

Enable allow_attributes lint for arrow-arith (#10595)

I'll work on enabling clippy::allow_attributes for the parquet-geospatial crate

Enable `allow_attributes` lint for `parquet-geospatial` (#10602)

I'd like to take the parquet-variant crate portion. I plan to enable clippy::allow_attributes for that crate and replace its single allow(unused) with an appropriately scoped expect.

I will take the arrow-data crate portion. I plan to enable clippy::allow_attributes for that crate, replace its single active Clippy allow with an expect, and run the crate-specific Clippy, tests, and formatting checks.