lmkd: Add zoneinfo and meminfo parsing routines

/proc/zoneinfo and /proc/meminfo contain information necessary for lmkd
to assess system memory state. Add routines to parse these files.


Bug: 77299493
Bug: 75322373
Merged-In: Ie7d80bbb81fd0d2fc0629f6f678e6afc97fed1f6
Change-Id: Ie7d80bbb81fd0d2fc0629f6f678e6afc97fed1f6
Signed-off-by: Suren Baghdasaryan <surenb@google.com>