Add silu operator

[voltjia]

pytest output:

============================= test session starts ==============================
platform linux -- Python 3.10.12, pytest-8.3.3, pluggy-1.5.0
rootdir: /home/huangjiacheng/ntops
configfile: pyproject.toml
plugins: cov-6.0.0
collected 270 items

tests/test_abs.py ........                                               [  2%]
tests/test_add.py ........                                               [  5%]
tests/test_addmm.py ..                                                   [  6%]
tests/test_bitwise_and.py ................                               [ 12%]
tests/test_bitwise_not.py ................                               [ 18%]
tests/test_bitwise_or.py ................                                [ 24%]
tests/test_bmm.py ..                                                     [ 25%]
tests/test_clamp.py ........                                             [ 28%]
tests/test_cos.py ........                                               [ 31%]
tests/test_div.py ........                                               [ 34%]
tests/test_dropout.py ........                                           [ 37%]
tests/test_eq.py ........                                                [ 40%]
tests/test_exp.py ........                                               [ 42%]
tests/test_ge.py ........                                                [ 45%]
tests/test_gelu.py ........                                              [ 48%]
tests/test_gt.py ........                                                [ 51%]
tests/test_isinf.py ........                                             [ 54%]
tests/test_isnan.py ........                                             [ 57%]
tests/test_le.py ........                                                [ 60%]
tests/test_lt.py ........                                                [ 63%]
tests/test_mm.py ..                                                      [ 64%]
tests/test_mul.py ........                                               [ 67%]
tests/test_ne.py ........                                                [ 70%]
tests/test_neg.py ........                                               [ 73%]
tests/test_pow.py ........                                               [ 76%]
tests/test_relu.py ........                                              [ 79%]
tests/test_rsqrt.py ........                                             [ 82%]
tests/test_sigmoid.py ........                                           [ 85%]
tests/test_silu.py ........                                              [ 88%]
tests/test_sin.py ........                                               [ 91%]
tests/test_softmax.py ........                                           [ 94%]
tests/test_sub.py ........                                               [ 97%]
tests/test_tanh.py ........                                              [100%]

======================= 270 passed in 248.50s (0:04:08) ========================