[vulkan] fix some broken tests in vulkan_api_test (#80962)
FIxes all the currently broken tests in `vulkan_api_test`.
* For the permute tests, removes the case where the dims are not permuted. This causes some exception later on due the returned tensor being an aliased version of the input, but this breaks things since Vulkan tensors are opaque and thus do not have strides
* Added `c10::InferenceMode mode;` to softmax test
* Fixed a small bug in the threshold shader that will sometimes set the output to 0
* Added a custom checking method of hardswish and threshold. Due to numerical differences, inputs close to the clamp threshold may either be 0 or equal to the input. This causes standard error checking to fail as a high delta will be detected.
Differential Revision: [D37383285](https://our.internmc.facebook.com/intern/diff/D37383285/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/80962
Approved by: https://github.com/manuelcandales
