xfs: prepare refcount btree cursor tracepoints for realtime

xfs: prepare refcount btree cursor tracepoints for realtime

Rework the refcount btree cursor tracepoints in preparation to handle the
realtime refcount btree cursor.  Mostly this involves renaming the field to
"refcbno" and extracting the group number from the cursor when possible.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>