delaunayn simplex check consistency and performance improvement (bug #60818) * delaunayn.m: Apply consistent volume calculation across all trivial simplex removal code paths. Vectorize 3D simplex removal code path and minimize function calls within >3D loop for performance improvement. Update FIXME note for future performance improvement. Add input type validation checks. Add BISTs for dimensions other than 2D, simplex removal, and input validation. * etc/News.8.md: Describe function improvements under General Improvements.

## recursive_nest.m
function x = recursive_nest ()
  global recursive_nest_inc = 1
  x = 5;
  f (20);

  function f (n)
    if (n > 0)
      x = x + recursive_nest_inc;
      f (n - 1);
    end
  endfunction
endfunction