lmkd: Introduce support for legacy kill algorithm that uses minfree levels

Add ability to switch to the algorithm used by lowmemorykiller driver
for determining when to kill. It uses minfree levels to decide at which
levels of free memory and file cache to kill a process. oom_adj_score
is also determined by comparing current memory resources against minfree
levels.
ro.lmk.use_minfree_levels property is introduces for switching into this
mode. By default it is disabled.

Bug: 77299493
Bug: 75322373
Change-Id: I6b51972951026854a079fcda33d6786b7ed035e4
Signed-off-by: Suren Baghdasaryan <surenb@google.com>