(Part 1) Use new socket schema with statsd tests

Moving statsd tests to the new socket schema.

Note: When initializing LogEvents with constructor
LogEvent::LogEvent(int32_t uid, int32_t pid), make sure to use uid of 0
and pid of 0 for LogEvents that will flow from StatsLogProcessor to
MetricsManager to MetricProducer. Otherwise, these LogEvents will not
have an allowed log source.

Test: bit statsd_test:*
Bug: 149590301
Change-Id: Ic6fba5b299da1816d690079bd445df0fc1b70995