[CMake] Split caffe2::cudnn into public and private (#59721)
Summary:
This is only important for builds where cuDNN is linked statically into libtorch_cpu.
Before this PR PyTorch wheels often accidentally contained several partial copies of cudnn_static library.
Splitting the interface into header only (cudnn-public) and library+headers(cudnn-private) prevents those from happening.
Preliminary step towards enabling optional linking whole cudnn_library to workaround issue reported in https://github.com/pytorch/pytorch/issues/50153
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59721
Reviewed By: ngimel
Differential Revision: D29000967
Pulled By: malfet
fbshipit-source-id: f054df92b265e9494076ab16c247427b39da9336
