From discussion with @Chillee and @bdhirsh.

1. torch_dispatch mode should have a flag for if it accepts HOPs or not. If it does, then the HOP should get passed into the __torch_dispatch__.
2. We should give HOPs similar properties to ops. That is, they should have a .tag, the .opoverload field should probably point back at itself, etc.
3. HOPs should take in a flag for if they're "passthrough" or "operator like". Maybe we can give generic handling for the passthrough HOPs x torch_dispatch stuff (but open question as to how this actually works).

cc @ezyang @gchanan @kadeng @msaroufim @chauhang @penguinwu @ydwu4 @bdhirsh @yf225