[CI] Install `pytorch-cuda` for conda testing (#94852)
Also, install it from the nightly channel, if `TORCH_CONDA_BUILD_FOLDER` is set to nightly
Discovered after doing a bit more GPU smoke testing
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94852
Approved by: https://github.com/atalman, https://github.com/Skylion007
