xfs_scrub: fix licensing and copyright notices [v24.5]

Fix various attribution problems in the xfs_scrub source code, such as
the author's contact information, out of date SPDX tags, and a rough
estimate of when the feature was under heavy development.  The most
egregious parts are the files that are missing license information
completely.

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