selftests/damon: add python and drgn-based DAMON sysfs test

selftests/damon: add python and drgn-based DAMON sysfs test

Add a python-written DAMON sysfs functionality selftest.  It sets DAMON
parameters using Python module _damon_sysfs, reads updated kernel internal
DAMON status and parameters using a 'drgn' script, namely
drgn_dump_damon_status.py, and compare if the resulted DAMON internal
status is as expected.  The test is very minimum at the moment.

Link: https://lkml.kernel.org/r/20250628160428.53115-4-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>