Function read_dense_deltas

fn read_dense_deltas<T>(
    cursor: &mut Cursor<'_>,
    deltas: &mut [T],
    f: impl FnMut(&mut T, i32),
) -> Result<(), ReadError>

This is basically a manually applied loop unswitching optimization for reading deltas. It reads each typed run into a slice for processing instead of handling each delta individually with all the necessary branching that implies.