message: Remove some integer conversion checks in ldl
  For these checks it is quite clear they can be converted to usize, as
  they were converted from usize before.
diff: @@ -502,7 +502,7 @@ where
  y_workspace[inner_ind] = y_workspace[inner_ind] + val;
  let mut i = inner_ind;
  pattern_workspace.clear_left();
  - while flag_workspace[i].index() != k {
  + while flag_workspace[i].index_unchecked() != k {
  pattern_workspace.push_left(I::from_usize(i));
  flag_workspace[i] = I::from_usize(k);
  i = parents.get_parent(i).expect("enforced by ldl_symbolic");
  @@ -515,7 +515,7 @@ where
  diag[k] = y_workspace[k];
  y_workspace[k] = N::zero();
  'pattern: for &i in pattern_workspace.iter_right() {
  - let i = i.index();
  + let i = i.index_unchecked();
  let yi = y_workspace[i];
  y_workspace[i] = N::zero();
  let p2 = (l_colptr[i] + l_nz[i]).index();
  