Add aten::detach NNAPI converter (#58543)
Summary:
* Add support for aten::detach op in the NNAPI model converter as a no-op
* Also add flexible op support for add_pointwise_simple_unary_op
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58543
Test Plan: pytest test/test_nnapi.py::TestNNAPI::test_detatch
Reviewed By: anshuljain1
Differential Revision: D28531942
fbshipit-source-id: 4387dbbbadd8ce6b690841f3a903e68a380b849d
