Enhancement: Allow excluding online-only cloud files (e.g. OneDrive)

Restic treated OneDrive Files On-Demand as though they were regular files
for the purpose of backup which caused issues with VSS, could make backup
incredibly slow (as OneDrive attempted to download files), or could fill
the source disk (e.g. 1TB of files in OneDrive on a 500GB disk).
Restic now allows the user to exclude these files when backing up with
the `--exclude-cloud-files` switch.

https://github.com/restic/restic/issues/3697
https://github.com/restic/restic/issues/4935
https://github.com/restic/restic/pull/4990