Move service-statsd to updatable system server jar

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 by moving it from
PRODUCT_SYSTEM_SERVER_JARS to PRODUCT_UPDATABLE_SYSTEM_SERVER_JARS

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: Ia261ea79b2a46a4cc709e1b7dd072de15e17571e