mm/damon/sysfs: split out schemes directory implementation to separate file

DAMON sysfs interface for 'schemes' directory is implemented using about
one thousand lines of code.  It has no strong dependency with other
parts of its file, so split it out to another file for better code
management.

Link: https://lkml.kernel.org/r/20221026225943.100429-11-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>