Function row_selection_from_row_ranges_exact 

pub(crate) fn row_selection_from_row_ranges_exact(
    row_ranges: impl Iterator<Item = Range<usize>>,
    total_row_count: usize,
) -> RowSelection

Like row_selection_from_row_ranges but guarantees the resulting selection covers exactly total_row_count rows by appending a trailing skip if needed.

Required when the result is used as the inner operand of [RowSelection::and_then], because and_then expects the inner selection to account for every row selected by the outer one.