Support fetching world and other init data from S3

[mstarostik]

Enhancement Type

Improve an existing feature

Describe the enhancement

It would be great if all features that support downloading from a URL or container path, e.g. WORLD, OPS_FILE, WHITELIST_FILE, ICON, etc. supported getting the respective files from a (private) S3 or bucket or other compatible object storage.
An easy workaround is proxying via nginx-s3-gateway or similar, but builtin support seems more straightforward.

Thanks for considering!

[itzg]

Great idea!