xfs: random fixes

Here's a handful of bug fixes for 5.12 and 5.13.  The first one fixes a
bug in quota accounting on idmapped mounts; the second avoids a buffer
deadlock in bulkstat/inumbers if the inobt is corrupt; and the third
fixes a mount hang if mount fails after creating (or otherwise dirtying)
the quota inodes.

Also included are some minor fixes to the scrub code to make sure that
we report the scrub state completely, tighten some of the checks to use
precomputed values instead of absolute maximum.  Finally, there are some
small code cleanups.