wip: use torch from a wheel

[rickeylev]

Using torch from a wheel will eliminate the ~20 minutes it takes to build from source.

A custom repo rule is used to replicate the structure that python_init_repositories
expects (a directory with a dist/ folder with a wheel) to add the whl file
into the requirements.txt files.

TODO:

• Handle different builds (cuda, nightly, etc). There thousands of pytorch wheels.
  Unclear which combinations need to be pulled.

Work towards #9173

[bhavya01]

Thanks for looking into this. It will helpful for #9173

[rickeylev]

Thanks! There's a couple questions I have that would help me figure out next steps:

1. Can the ability to use a pytorch source checkout be removed entirely? It's easy to allow using a locally built wheel still.
2. The ts_native_functions yaml and cpp files aren't in the wheel. Are the actually needed? From my local building, their absence hasn't resulted in any errors.
3. Which versions and configurations of pytorch are needed? In order to use wheels, we'll need to specify them by URL (either via environment variables, or having a list in a .bzl file)