Implement min, max, sum for run-end-encoded arrays.

[brunal]

Efficient implementations:

• min & max work directly on the values child array.
• sum folds over run lengths & values, without decompressing the array.

In particular, those implementations takes care of the logical offset & len of the run-end-encoded arrays. This is non-trivial:

• We get the physical start & end indices in O(log(#runs)), but those are incorrect for empty arrays.
• Slicing can happen in the middle of a run. For sum, we need to track the logical start & end and reduce the run length accordingly.

Finally, one caveat: the aggregation functions only work when the child values array is a primitive array. That's fine ~always, but some client might store the values in an unexpected type. They'll either get None or an Error, depending on the aggregation function used.

This feature is tracked in #3520.

[brunal]

Note that in a future MR, I'm likely to move most of ree::fold() into run_array.rs, providing an iterator over (run_idx_start, run_idx_end, value), and use that in cmp.rs.

[brunal]

I'm not handling null values properly when computing sums. Back to draft.

[brunal]

Thank you for the review. values_slice/sliced_values are very helpful and clean up nicely the implementations. They do have a performance downside (looking for physical indices twice) but that seems worth the clean code.