Geo file sync should use persistent HTTPS connections to the primary

I'm not sure what's happening at the moment. Geo::FileDownloadDispatchWorker enqueues GeoFileDownloadWorker jobs, keeping a configurable number of them enqueued all at once. If each of the latter maintains its own HTTPS connection to the primary, this is inefficient and will be slowing us down as we'll have to pay the HTTPS connection establishment fee per file.

Instead, we should be able to maintain a pool of long-lived HTTPS connections and send requests via that pool