Enhance the torch.pow testcase for the complex scalar base (#47101)
Summary:
Related https://github.com/pytorch/pytorch/issues/45259
This PR is to address the https://github.com/pytorch/pytorch/pull/45259#discussion_r514390664
- leverage the `make_tensor` function to generate a random tensor as the exponent, preventing the full zeros for the integer exponent.
- add some special cases for the zero exponents and the `1 + 0j` base.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47101
Reviewed By: mruberry
Differential Revision: D24682430
Pulled By: zou3519
fbshipit-source-id: f559dc0ba08f37ae070036fb25a52ede17a24149
