[autodiff] Set default seed only for scalar parameter to avoid silent unexpected results (#5287)
[autodiff] Set default seed only for scalar parameter to avoid silent unexpected results (#5287)

* [autodiff] Set default seed only for scalar parameter to avoid slient unexpected results

* update
yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi