lmkd: Add meminfo logging after each kill for easy troubleshooting

While troubleshooting memory pressure related issues it's hard to get a
good view of the memory state when lmkd kill happens. Logging relevant
information from /proc/meminfo file that was used to make a kill decision
is very helpful for further analysis. To do this efficiently we are using
Android Logger event library functions and log the data used for kill
decision after the kill signal was issued.

Test: Run lmkd_unit_test and logcat -b events -v descriptive
Change-Id: Id5de41b9d91a04dd5d3eb9b85d4e1babe9755628
Signed-off-by: Suren Baghdasaryan <surenb@google.com>