xfs: store rtgroup information with a bmap intent

xfs: store rtgroup information with a bmap intent

Make the bmap intent items take an active reference to the rtgroup
containing the space that is being mapped or unmapped.  We will need
this functionality once we start enabling rmap and reflink on the rt
volume.  Technically speaking we need it even for !rtgroups filesystems
to prevent the (dummy) rtgroup 0 from going away, even though this will
never happen.

As a bonus, we can rework the xfs_bmap_deferred_class tracepoint to use
the xfs_group object to figure out the type and group number, widen the
group block number field to fit 64-bit quantities, and get rid of the
now redundant opdev and rtblock fields.

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