Use `setup-python` just for caching

[cecheta]

Description: It would be good to be able to use this action just to cache dependencies, without also downloading Python. For example:

- uses: actions/setup-python@v5
  with:
    cache: pip

This currently doesn't work, because the version is not set.

You can do something similar with setup-node, for example:

- uses: actions/setup-node@v4
  with:
    cache: npm

Justification: It would be able to use the existing logic in this action to cache dependencies, instead of having to use the cache action manually.

Are you willing to submit a PR? Yes