Change test_python_actors test parameter to enum (#1441)

Summary:
Pull Request resolved: #1441

Currently these tests cover 2 versions:
1. V0
2. Rust V1 + retrofit v0 multicasting.

In D83838109, I want to add another version, Rust V1 + native v1 multicasting (added in D83780557).  This diff changes the test parameter to a enum so it is easier to add the 3rd one later.

Reviewed By: samlurye

Differential Revision: D83784078

fbshipit-source-id: 6129c344e29cac106d45ce8f32c435a9ae227953

Author: pzhan9