CI: Update FreeBSD versions and handling

[mcmilk]

Update FreeBSD versions:

• add FreeBSD 15.0-STABLE
• add FreeBSD 16.0-CURRENT

In commits - you may specify which type of CI should run:

• ZFS-CI-Type: quick
• ZFS-CI-Type: linux
• ZFS-CI-Type: freebsd
• ZFS-CI-Type: full (should maybe renamed to default, cause full would normally mean everything)

This PR did run only FreeBSD tests, because of this line:
ZFS-CI-Type: freebsd

The current PR should runs only linux based tests via:
ZFS-CI-Type: linux

Motivation and Context

Current FreeBSD 15 tests are always red :/

How Has This Been Tested?

Within my private repo I tested a bit - but this PR will hopefully run only FreeBSD tests now .. this is tested by this PR ;)

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)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• 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)

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.