selftests/damon/_damon_sysfs: support quota goals

Patch series "selftests/damon: add DAMOS quota goal test".

Extend DAMON selftest-purpose sysfs wrapper to support DAMOS quota goal,
and implement a simple selftest for the feature using it.


This patch (of 2):

The DAMON sysfs test purpose wrapper, _damon_sysfs.py, is not supporting
quota goals.  Implement the support for testing the feature.  The test
will be implemented and added by the following commit.

Link: https://lkml.kernel.org/r/20240502172718.74166-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240502172718.74166-2-sj@kernel.org


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