Docs/mm/damon: move the list of DAMOS actions to design doc

DAMOS operation actions are explained nearly twice on the DAMON usage
document, once for the sysfs interface, and then again for the debugfs
interface.  Duplication is bad.  Also it would better to keep this kind of
concept level details in design document and keep the usage document small
and focus on only the usage.  Move the list to design document and update
usage document to reference it.

Link: https://lkml.kernel.org/r/20240217005842.87348-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>