xfs: rework online fsck incore bitmap

In this series, we make some changes to the incore bitmap code: First,
we shorten the prefix to 'xbitmap'.  Then, we rework some utility
functions for later use by online repair and clarify how the walk
functions are supposed to be used.

Finally, we use all these new pieces to convert the incore bitmap to use
an interval tree instead of linked lists.  This lifts the limitation
that callers had to be careful not to set a range that was already set;
and gets us ready for the btree rebuilder functions needing to be able
to set bits in a bitmap and generate maximal contiguous extents for the
set ranges.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
-----BEGIN PGP SIGNATURE-----
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=mNyj
-----END PGP SIGNATURE-----