Enable block_cloning tests on FreeBSD.

[pjd]

Motivation and Context

We want as many tests as possible to run on as many platforms as possible.
The following changes allow most of the block_cloning tests to be exercised also on FreeBSD.

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)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)
• Tests

Checklist:

• My code follows the OpenZFS 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.

[pjd]

This PR requires changes to the clonefile tool that are part of the #15631 PR.

[behlendorf]

@pjd it looks like this just needs a rebase.

[behlendorf]

@pjd I went ahead and opened #15749 with a clean rebase of this for the CI.

[pjd]

@pjd I went ahead and opened #15749 with a clean rebase of this for the CI.

I'm sorry, Brian, I missed your previous comment about rebase!