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.

Note this is still a bit hacky at the moment by just going beyond the AG
arrays and not fully supporting the unknown state for RT allocation yet.
The next patch will clean this up.

All this should be fixable.

Large parts of the code are based on patches from Darrick J. Wong.

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>