Add support for redirected shadow storage

[antwise]

I've made a little and quick test program using libvshadow in C++ that does the following:

 libvshadow_volume_initialize
 libvshadow_volume_open_wide
 libvshadow_volume_get_number_of_stores

 for store in stores
      libvshadow_volume_get_store
      libvshadow_store_get_copy_identifier
      libvshadow_store_free
 libvshadow_volume_free

For every call there are appropriate error control routines

 libvshadow_error_sprint

The environment:

• I've built the library using Visual Studio 2010 and run in Windows 7: everything works fine
• I'm using this little program on a spare live volume so I pass something like \?\Volume{066cb78e-f66a-4d00-9baf-28301ed28265} libvshadow_volume_open_wide and it works well
• I use vssadmin to create and delete snapshots

The experiment:

• After this I redirect shadowstorage of volume E on D and D on E, than create shadows.
• libvshadow_store_get_copy_identifier fails.

Remarks:

Its appear because records with type=2 stored on original volume, and records with type=3 on target volume.

Attached logs: libvshadow_D.log

[joachimmetz]

At the moment libvshadow only supports snapshots that are on the same volume. I'll add a note to the README to indicate that "redirected storage is not support", and when time permits, I'll have a closer look to what it would take to support "redirected storage".

[joachimmetz]

Note to self create test files https://github.com/dfirlabs/vss-specimens

[joachimmetz]

Left a note in https://github.com/dfirlabs/vss-specimens/blob/main/Notes.md#redirected-shadowstorage on how to create "redirected shadowstorage". Appears to be a Windows server only feature and only appears to work for non Windows virtualized disks (VHD/VHDX)