Avoid making purl2vcs calls in the index_packages view function

- [ ] `index_packages` is meant for bulk indexing of packages asynchronously. Since purl2vcs involves network call, it should not be called in the view function. Instead, purl2vcs should be called while processing the PriorityResourceURI.
- [ ] Also, currently purl2vcs is only called when reindexing is requested. It should also be called when indexing new packages.