selftests/damon: add a test for DAMOS quota goal

Add a selftest for DAMOS quota goal.  It tests the feature by setting a
user_input metric based goal, change the current feedback, and check if
the effective quota size is increased and decreased as expected.

Link: https://lkml.kernel.org/r/20240502172718.74166-3-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>