lmkd: Add support for psi monitors

With new psi monitor support in the kernel lmkd can use it to register
custom pressure levels. Add lmkd support for psi monitors when they are
provided by the kernel and use them by default. When kernel does not
support psi lmkd will fall back to vmpressure usage.
Add ability to poll memory status after the initial psi event is triggered
because kernel throttles psi memory pressure events to one per PSI tracking
window (currently set to 1sec). Current implementation polls every 200ms
for 1sec duration after the initial event is triggered.
If ro.lmk.use_psi is set to false psi logic will be disabled even when psi
is supported in kernel.

Bug: 111308141
Test: lmkd_unit_test
Change-Id: I685774b176f393bab7412161773f5c9af51e0163
Signed-off-by: Suren Baghdasaryan <surenb@google.com>