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.
With this interface it is possible to wrap the current support for snapshots and USN and simplify the enumeration.
This makes a number of assumptions into fields such as `IsMetaEntry` and `IsRootEntry` that removes code that was checking for various properties.
This first commit has support for VSS and USN as well as "naked" files, keeping feature parity.
There is also an experimental support for loading a backend-as-a-source. The support for this is currently limited as the backends need to be extended to support a folder concept.