Add log source filtering in statsd to filter out spams.

+ Add log source whitelist in StatsdConfig
+ Some changes in UidMap API. Listener needs to be wp instead of sp.
+ Update dogfood app config to have log source
+ Increase the stats service thread pool size to 10 (9+1).

TODO: add unit tests(b/70805664). This unit test takes some time to write.

Test: statsd_test & manual

Change-Id: I129b1cc13db5114db7417580962bd7cc4438519d