xfs: fix integer overflows in the fsmap rtbitmap and logdev backends

It's not correct to use the rmap irec structure to hold query key
information to query the rtbitmap because the realtime volume can be
longer than 2^32 fsblocks in length.  Because the rt volume doesn't have
allocation groups, introduce a daddr-based record filtering algorithm
and compute the rtextent values using 64-bit variables.  The same
problem exists in the external log device fsmap implementation, so use
the same solution to fix it too.

After this patch, all the code that touches info->low and info->high
under xfs_getfsmap_logdev and __xfs_getfsmap_rtdev are unnecessary.
Cleaning this up will be done in subsequent patches.

Fixes: 4c934c7d ("xfs: report realtime space information via the rtbitmap")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>