CHROMIUM: Add implementation of MGLRU in sysfs

debugfs is disabled by default for security reasons. This CL removes the
dependency of lru_gen on debug and adds new implemenetation using sysfs.
Path changes from /sys/kernel/debug/lru_gen to /sys/kernel/mm/lru_gen/admin

BUG=b:241321277
TEST=Manual testing on DUT
TEST=cat /sys/kernel/mm/lru_gen/admin && /sys/kernel/debug/lru_gen
TEST=same result before and after dropping the pages

Signed-off-by: Bryan Yu <yuholong@google.com>
Change-Id: I62d8cbd4b8b614dbe6da08c4a11d7c99e30bb5ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3839069


Reviewed-by: Yu Zhao <yuzhao@chromium.org>
Reviewed-by: Suleiman Souhlal <suleiman@chromium.org>