Add keystore API for metrics re-routing.

Keystore2 atoms need to be routed to statsd via a proxy.
The proxy needs to call this API in order to pull metrics from
keystore.

Bug: 188590587
Test: Statsd Testdrive script
Merged-In: I28f8675fe5467b0760418c4d2d87808e45657be1

Change-Id: I28f8675fe5467b0760418c4d2d87808e45657be1
33 files changed