Function update_distinct_values_seen 

fn update_distinct_values_seen(
    array: &dyn Array,
    non_null_indices: &[usize],
    seen: &mut HashSet<u64>,
)

Hash the non-null values in array (at non_null_indices) into seen.

Handles primitive, boolean, fixed-size-binary, and variable-length (Utf8/Binary) arrays. Unsupported types are silently skipped, leaving seen unchanged for those values (NDV is best-effort).