Update metadata sync to support info.json

[rwilso03]

With info.json download support having been added, one capability that I see missing is the ability to use the "sync-missing-metadata" management function to fill in the missing json files from existing media files. This function currently syncs missing nfo and thumbnails, but does not test to see if the json files exist and build them as needed.

[meeb]

This might be possible, I'll look into it. The info.json style output is directly written by yt-dlp so for this requested feature to be possible yt-dlp needs to support writing out only the info.json data to a file and no other operations for a sync-missing-info-data to function. If it's possible I'll pop it on the wishlist.