CPack/DMG: Add explicit option to use CPACK_RESOURCE_FILE_LICENSE for SLA

Since macOS 12.0, the ``hdiutil udifrez`` and ``hdiutil udifderez``
commands to embed and extract resources in a disk image are deprecated.
The CPack DragNDrop Generator uses these to attach the SLA specified by
the `CPACK_RESOURCE_FILE_LICENSE` option.  Since that option is shared
by multiple CPack generators, we cannot deprecate it.  Instead, add an
explicit option to control the behavior.  This will give projects a way
to package on future macOS versions that remove the commands.

In order to provide a long-term transition away from attaching SLAs to
disk images, update `cpack` to default this behavior to OFF.  To retain
compatibility for CMake projects, teach the CPack module to default the
option to ON.  Later a policy can be added to change the default.

Issue: #22978
38 jobs for !6876 with cpack-dmg-sla in 36 minutes and 5 seconds (queued for 5 seconds)
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