Add pow 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 254 items

tests/test_abs.py ........                                               [  3%]
tests/test_add.py ........                                               [  6%]
tests/test_addmm.py ..                                                   [  7%]
tests/test_bitwise_and.py ................                               [ 13%]
tests/test_bitwise_not.py ................                               [ 19%]
tests/test_bitwise_or.py ................                                [ 25%]
tests/test_bmm.py ..                                                     [ 26%]
tests/test_clamp.py ........                                             [ 29%]
tests/test_cos.py ........                                               [ 33%]
tests/test_div.py ........                                               [ 36%]
tests/test_dropout.py ........                                           [ 39%]
tests/test_eq.py ........                                                [ 42%]
tests/test_exp.py ........                                               [ 45%]
tests/test_ge.py ........                                                [ 48%]
tests/test_gelu.py ........                                              [ 51%]
tests/test_gt.py ........                                                [ 55%]
tests/test_isinf.py ........                                             [ 58%]
tests/test_isnan.py ........                                             [ 61%]
tests/test_le.py ........                                                [ 64%]
tests/test_lt.py ........                                                [ 67%]
tests/test_mm.py ..                                                      [ 68%]
tests/test_mul.py ........                                               [ 71%]
tests/test_ne.py ........                                                [ 74%]
tests/test_neg.py ........                                               [ 77%]
tests/test_pow.py ........                                               [ 81%]
tests/test_relu.py ........                                              [ 84%]
tests/test_rsqrt.py ........                                             [ 87%]
tests/test_sigmoid.py ........                                           [ 90%]
tests/test_sin.py ........                                               [ 93%]
tests/test_softmax.py ........                                           [ 96%]
tests/test_tanh.py ........                                              [100%]

======================= 254 passed in 239.92s (0:03:59) ========================