mm/damon/sysfs-schemes: implement schemes/tried_regions directory

mm/damon/sysfs-schemes: implement schemes/tried_regions directory

For efficient and simple query-like DAMON monitoring results readings and
deep level investigations of DAMOS, DAMON kernel API
(include/linux/damon.h) users can use 'before_damos_apply' DAMON callback.
However, DAMON sysfs interface users don't have such option.

Add a directory, namely 'tried_regions', under each scheme directory to
use it as the interface for the purpose.  Note that this commit is
implementing only the directory but the data filling.

After the data filling change is made, users will be able to signal DAMON
to fill the directory with the regions that corresponding scheme has tried
to be applied.  By setting the access pattern of the scheme, users could
do the efficient query-like monitoring.

Link: https://lkml.kernel.org/r/20221101220328.95765-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>