[SETUPLIB][USETUP] Factor out the usage of FS provider structures.

Similarly to FMIFS this structure should be private. Instead file-system
names are passed to the helper functions, allowing to use the names
returned by the FS drivers. The names are then internally mapped to the
corresponding FS providers.

In particular this allows to handle the "RAW" file-system and to assign
the 'Unformatted' flag to partitions having this FS.

Finally this helps us refining the checks performed to see whether the
current "active" system partition uses a supported file-system.

base/setup/usetup/chkdsk.h

@@ -28,7 +28,6 @@
 NTSTATUS
 ChkdskPartition(
     IN PUNICODE_STRING DriveRoot,
-    /*IN PFILE_SYSTEM_ITEM FileSystemItem*/
-    IN PFILE_SYSTEM FileSystem);
+    IN PCWSTR FileSystemName);
 
 /* EOF */