This PR adds support for using Box, Dropbox, GoogleDrive, SharepointV2, MicrosoftGroups, and OneDrive as remote sources.
For GoogleDrive, this requires full permissions and not just the regular OAuth access token.
Also extended S3 and SMB to actually look up a file if requested, which makes it possible to rely on the backup exclusion files, even when using remote sources. (SSH/SFTP does not currently support this).
This PR updates existing backends to implement the `IRenameEnabledBackend` interface, allowing for more efficient file renaming operations. The implementation varies by backend, with some using native rename operations and others falling back to copy-and-delete patterns.
