The first step towards adding a guardrail.

Added a malloc debug cmd to find memory leak and where
the most heap allocations are with backtrace.

More info: malloc_debug/README.md

The util class is borrowed from audio server.

Usage:

adb shell stop
adb shell setprop libc.debug.malloc.program statsd
adb shell setprop libc.debug.malloc.options backtrace
adb shell start
adb shell cmd stats meminfo

Also,

adb shell dumpsys meminfo [statsd_pid]

also gives you the overall summary of the memory usage.

Test: manual

Change-Id: I4eb4167466a748ea0c3d9fd39e45d9900bc00fc2