xfs_repair: support realtime groups

xfs_repair: support realtime groups

Make repair aware of multiple rtgroups.  This now uses the same code as
the AG-based data device for block usage tracking instead of the less
optimal AVL trees and bitmaps used for the traditonal RT device.  This
is done by introducing similar per-rtgroup space tracking structures as
we have for the AGs.

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