Update python_info aspect to accommodate Python targets that only have rules_python providers

[mnoah1]

As the Python rules are gradually phasing out use of the builtin PyInfo provider in favor of the ones from rules_python, there could be cases where a repository is on a Bazel version lower than 8, but the built in PyInfo is still missing from a given target.

In our repo's case, we are in the process of migrating to rules_py, which uses the rules_python providers only (aspect-build/rules_py#311), and not the built in ones.

This change now covers the following scenarios, allowing Bazel 7 repositories to have either the builtin or rules_python providers in their targets:

• Bazel <7 - continue to use built in providers only [existing behavior]
  • rules_python won't always be available in Bazel <7 workspaces, so supporting this here would have added additional complexity for a relatively unlikely use case
• Bazel 7 - if builtin providers are missing from a target, use rules_python providers
• Bazel 8 - rules_python providers only [existing behavior]

[mnoah1]

It looks like all the e2e tests pass with this change, but I'm seeing a failure in the [analysis] Qodana android-forked-bazel-rules-project step with error: found 'project contains no modules' in the build log. I don't think it seems related to my change but I'm not quite sure - could you help me verify?

[mnoah1]

Hi @agluszak - could you give this one another look when you have a chance? Thanks.