xfs_scrub: retest metadata across scrub groups after a repair

xfs_scrub: retest metadata across scrub groups after a repair

Certain types of metadata have dependencies that cross scrub groups.
For example, after a repair the part of realtime bitmap corresponding to
a realtime group, we potentially need to rebuild the realtime summary to
reflect the new bitmap contents.  The rtsummary is a separate scrub group
(metafiles) from the rgbitmap (rtgroup), which means that the rtsummary
repairs must be tracked by a separate scrub_item.

Create the necessary dependency table and code to make these kinds of
cross-group validations possible.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>