fix asserts in cuda code (#39047)
Summary:
Gets rid of some in-kernel asserts where they can be replaced with static_asserts
Replaces bare in-kernel `assert` in one case with `CUDA_KERNEL_ASSERT` where necessary
replaces host code `assert`s with `TORCH_INTERNAL_ASSERT`
Another group of asserts is in fractional max pooling kernels which should be fixed regardless https://github.com/pytorch/pytorch/issues/39044, the problems there are not just asserts.
I've audited remaining cases of in-kernel asserts, and they are more like `TORCH_INTERNAL_ASSERT`, so they should not happen with invalid user data. I think it's ok to leave them as is.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39047
Differential Revision: D21750392
Pulled By: ngimel
fbshipit-source-id: e9417523a2c672284de3515933cb7ed166e56719
