fix: Properly handle nested directories in S3

[charmitro]

This fixes the issue with nested directories not being properly handled when using rclone with the S3 server. The fix implements a more accurate approach to directory listings that:

1. Correctly handles the hierarchical structure of directories
2. Properly applies S3 delimiter logic for nested paths
3. Ensures files in nested directories are correctly reported
4. Makes recursive copying work as expected

Added a test to verify recursive copy functionality.