[NNC] Fix lowering of aten::pow (#47795)
Summary:
NNC lowering of aten::pow assumes that the types of the exponent is either float or int cast to to float, which doesn't work great with double (or half for that matter).
Fixes https://github.com/pytorch/pytorch/issues/47304
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47795
Reviewed By: ZolotukhinM
Differential Revision: D24904201
Pulled By: nickgg
fbshipit-source-id: 43c3ea704399ebb36c33cd222db16c60e5b7ada5
