[FreeBSD only] ERESTART and TRAVERSE_VISIT_NO_CHILDREN have the same value

[avg-I]

System information

Type	Version/Name
Distribution Name	FreeBSD
Distribution Version	14.2 / any recent
Kernel Version	14.2
Architecture	any
OpenZFS Version	zfs-2.2.6-FreeBSD_g33174af15

Describe the problem you're observing

On FreeBSD ERESTART and TRAVERSE_VISIT_NO_CHILDREN have the same value of -1.
Both can be returned from traversal callbacks.
TRAVERSE_VISIT_NO_CHILDREN has special handling within the traversal code.
So, it's possible that ERESTART returned from a callback like dsl_scan_free_block_cb
would be handled as TRAVERSE_VISIT_NO_CHILDREN.

Describe how to reproduce the problem

I do not have a clear demonstrator but I suspect that the problem could be triggered
when destroying a large dataset such that dsl_scan_free_block_cb would have to return
ERESTART .

As a result traverse_dnode could skip remaining blocks under a dnode where ERESTART
is triggered.
Those blocks would be leaked.

Possible solution

Change value of TRAVERSE_VISIT_NO_CHILDREN to something even "more magic" to avoid
conflict with low numbered negative return values used in FreeBSD
(defined in errno.h).
For example, a value of -100 should work fine.