Conda package should support pillow-simd

🐛 Bug

torchvision Conda package, at least with v0.10.0, depends on pillow, which complicates using pillow-SIMD.

To Reproduce

Steps to reproduce the behavior:

1. Install torchvision with Conda.
2. Try to uninstall pillow, but would try to uninstall torchvision. Alternatively, you can do conda remove --force pillow to only remove it, but the environment will be in an inconsistent state. It's the best workaround AFAIK though.
3. Install pillow-SIMD.

Expected behavior

The expected behavior would be to be able to choose between pillow and pillow-SIMD, or be able to uninstall pillow without breaking things, and then install pillow-SIMD. After this, every time you try installing something with conda, it's gonna try to install pillow again.

Maybe pillow shouldn't be a dependency then? Maybe the ideal solution is to pillow-SIMD to provide a conda package called pillow, or something like that (or like a virtual package to support both?).

Start by reviewing the torchvision Conda package dependency metadata and reproducing the reported install, removal, and replacement sequence with pillow-SIMD. Done means users can choose pillow or pillow-SIMD without Conda reinstalling pillow or leaving the environment inconsistent.