StatsEventCompat

StatsEventCompat is a wrapper library that toggles between the old
logging scheme and the new logging scheme. It was designed particularly
for the DNS Resolver module and should not be used by others.

We will merge libstatspush_compat and libstatssocket_q in a future CL.

Test: m libstatspush_compat
Test: bit libstatspush_compat_test:* (passes on Q and R)
Bug: 145534143

Change-Id: Ib355031f3573101ea90bd8694861fbfc33b0c788
Merged-In: Idf35ccb6669798166475f08b2fbab40534b5db19