use new FreeBSD API to largely eliminate object locking

[mattmacy]

Propagate changes in HEAD that mostly eliminate object locking.

Motivation and Context

Description

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[adamdmoss]

A note for readers: this relates entirely to FreeBSD. That wasn't obvious to me from the description or title so I thought I'd point it out. :)

[codecov-io]

Codecov Report

Merging #10205 into master will decrease coverage by 13.61%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master   #10205       +/-   ##
===========================================
- Coverage   79.38%   65.77%   -13.62%     
===========================================
  Files         388      306       -82     
  Lines      123392   106102    -17290     
===========================================
- Hits        97953    69785    -28168     
- Misses      25439    36317    +10878     

Flag	Coverage Δ
#kernel	?
#user	65.77% <ø> (+0.26%)	⬆️

Impacted Files	Coverage Δ
module/zfs/objlist.c	0.00% <0.00%> (-100.00%)	⬇️
module/zfs/pathname.c	0.00% <0.00%> (-100.00%)	⬇️
include/sys/dmu_redact.h	0.00% <0.00%> (-100.00%)	⬇️
include/sys/dmu_traverse.h	0.00% <0.00%> (-100.00%)	⬇️
module/zfs/zfs_rlock.c	0.00% <0.00%> (-96.36%)	⬇️
module/lua/ltablib.c	2.34% <0.00%> (-95.32%)	⬇️
module/zfs/bqueue.c	0.00% <0.00%> (-94.45%)	⬇️
module/zcommon/zfs_deleg.c	0.00% <0.00%> (-92.46%)	⬇️
module/zfs/dmu_diff.c	0.00% <0.00%> (-87.88%)	⬇️
module/zfs/zcp_set.c	0.00% <0.00%> (-87.10%)	⬇️
... and 236 more

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