Enhancement: Ignore s3.storage-class for metadata if archive tier is specified

There is no official cold storage support in restic, use this option at your
own risk.

Restic always stored all files on s3 using the specified `s3.storage-class`.
Now, restic will store metadata using a non-archive storage tier to avoid
problems when accessing a repository. To restore any data, it is still
necessary to manually warm up the required data beforehand.

https://github.com/restic/restic/issues/4583
https://github.com/restic/restic/pull/4584
