Clean up Android prebuilt artifact path and verification (#6181)

Summary:
In main branch, use dated artifacts like https://ossci-android.s3.amazonaws.com/executorch/release/executorch-241002/executorch.aar In release branch, use something like release/0.4

Automate shasum check

Pull Request resolved: https://github.com/pytorch/executorch/pull/6181

Reviewed By: mergennachin

Differential Revision: D64261746

Pulled By: kirklandsign

fbshipit-source-id: 0c3e895eb44ed50cb009d8daff8b51b750a1dda5