Move service-statsd.jar into statsd apex

This moves StatsCompanionService into the statsd apex.
service-statsd.jar is no longer installed to system/framework, and is
instead installed to
/apex/com.android.os.statsd/javalib/service-statsd.jar.

Bug: 145923413
Test: make clean; make; vendor/google/tools/flashall and manual
inspection of jar locations
Test: made trivial update to SCS and bumped the version of the apex.
Then did: 1. make com.android.os.statsd 2. adb install
com.android.os.statsd 3. adb reboot. Verified that the change was
reflected via the apex update

Change-Id: I456a60d022d4286f47fe3dd5cd159de39897119e