Incorrect comment on arrow::compute::kernels::sort::sort_to_indices

[westonpace]

Describe the bug
The docs for arrow::compute::kernels::sort::sort state:

Floats are sorted using IEEE 754 totalOrder

The docs for arrow::compute::kernels::sort::sort_to_indices state:

For floating point arrays any NaN values are considered to be greater than any other non-null value

These are different, which I suppose is technically ok (though not very helpful). However, in practice, it seems that they both use total order.

To Reproduce

use std::sync::Arc;
use arrow_array::{ArrayRef, Float32Array};
pub fn main() {
    let pos_nan = f32::NAN;
    let neg_nan = -pos_nan;
    let zero = 0_f32;

    let vals: ArrayRef = Arc::new(Float32Array::from_iter_values(
        [zero, neg_nan, pos_nan].iter().copied(),
    ));
    // Prints NaN, 0.0, NaN -- matches the comment
    dbg!(arrow::compute::kernels::sort::sort(vals.as_ref(), None).unwrap());
    // Prints 1, 0, 2 -- matches total order, but not the comment
    dbg!(arrow::compute::kernels::sort::sort_to_indices(vals.as_ref(), None, None).unwrap());
}

Expected behavior
My personal preference would be to update the comment to reflect that both sorting methods use total order. If we can confirm that is the intention I can create a PR.

Additional context
N/A

[tustvold]

As you rightly identify the docs on sort_to_indices are out of date and should be updated

[tustvold]

label_issue.py automatically added labels {'arrow'} from #5033