Add retries to Artifactory calls

[briantist]

Have been starting to see cases where a sudden flood of connections (like in a CI with a big parallel matrix) causes calls to artifactory to fail, ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response')).

One way we could do this is with urllib3's Retry class, by ensuring we create a Session ourselves and passing it to ArtifactoryPath: https://github.com/devopshq/artifactory#session

We might need to be careful with this to ensure that everywhere we instantiate such an object we also use a proper session.

To that end, we could maybe subclass ArtifactoryPath with like GalactoryPath or whatever, that handles retryability.

---

Another option is to use a library like backoff to wrap calls we make. But I think that might not be the best option.