Add handling for multiple urls in fetch

[xx4h]

• change Download struct to list of urls
• add URLs to Fetch struct
• add new handler for Fetch Type "download_list" in Fetcher
• Type "download" and "default" will use list with single url
• Fetch will iterate through the urls and try them one by one until one is successful

[Saruspete]

Hello, Any update on this PR ? That would be nice when the softs change versions naming during their lifecycle, like fzf added the v in v0.54.0

Thanks a lot