This fixes the restore issues as all sources will now appear as if they were originally part of the source file system.
The backend implementation has now been simplified so the backends only return names of entries with no path information. Most backends already do this, but the S3 backends did not, so this was fixed as well.
This also clears up the interfaces, so the backend does not know about the `ISourceProviderEntry`. All mapping is done by the `BackendSourceProvider`, making it simpler to support other backends as sources.
Made the SMBShareConnection slightly more robust.
Introduced v2 List API to S3 backend, currently it retains v1 as the default.
Changed S3 backends to not recurse, potentially making smaller listings. This option can be disabled if it breaks things.
Added support for relative paths in the SSH backend.
This PR is the final change, where all backends are now purely implemented with async interfaces.
The code changes here replace the LIST call with an async version. This affect all backends (and then some) but the changes are mostly mechanical rewrites of the code.
In many places, the backeds were already prepared for async output, in other some glue was needed.
To reduce the scope of this change, some backends simply report a synchronous result as an async list.
Delay was caused by AWS library performing network queries when reading properties on the configuration object.
On top of this, the properties were read twice.
Unified reading+application of options between iDrive and AWS S3.