Trace downstream refs when fully optimizing services.jar

Add a hook to trace references from PRODUCT_SYSTEM_SERVER_JARS
that depend on the services.jar. This ensures that services.jar keeps
such references during optimization, avoiding the need to manually
specify and update associated keep rules.

Note that we only apply this to the FULL_SYSTEM_OPTIMIZE_JAVA case, as
1) downstream deps for such builds have been updated to references
services.impl, and 2) fully optimized services passes are far more
sensitive to downstream libs references, and stand to benefit the most
from auto-generated keep rules. A previous CL attempt landed but was
rolled back as not all downstream deps have been refactored to break
the cyclic dependency.

A follow-up change will remove existing hardcoded rules for certain
devices that are no longer necessary.

Bug: 212737576
Test: lunch wear + m + inspect proguard_configuration for services.jar
Flag: EXEMPT build refactor
Change-Id: I494228dabb829fe2a7b6224a5278aed70f661c31