Use Existing Setup Actions When Available

There are already a number of heavily optimized setup actions (e.g., [setup-python](https://github.com/marketplace/actions/setup-python)). Python, for example, can usually be installed at a given recent version more than an order of magnitude faster using the setup-python action than via asdf (when asdf cache misses or always if you aren't using caching). It would be interesting to add a new (default) mode where the official setup actions are used in lieu of the corresponding plugin when possible, which would probably imply a major version bump. There are currently [8 GitHub-authored setup actions](https://github.com/actions?q=setup), which is where I would propose stopping for the first iteration of this feature. There is a long tail of setup actions authored by other organizations, so I suggest that the asdf community add support for those incrementally in a self-serve fashion if desired. It would be necessary to be able to override the proposed default behavior in case one is testing an asdf plugin itself or requires extremely high fidelity between their development environment and their CI pipeline. Please let me know if anyone has any feedback on such a feature.

Start by reviewing the repository's existing GitHub Actions and asdf setup flow; the issue does not name specific files or tests. Define the supported GitHub-authored setup actions, the default-versus-override behavior, and how plugin testing remains possible. Done means the proposed setup actions work for the first-iteration cases with a documented fallback and validation path.

Written by the indexing model from the issue text.