afs: Improve afs_volume tracing to display a debug ID

afs: Improve afs_volume tracing to display a debug ID

Improve the tracing of afs_volume objects to include displaying a debug ID
so that different instances of volumes with the same "vid" can be
distinguished.

Also be consistent about displaying the volume's refcount (and not the
cell's).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20250224234154.2014840-9-dhowells@redhat.com/
Link: https://lore.kernel.org/r/20250310094206.801057-5-dhowells@redhat.com/