Use AssistedInject to allow guice to construct StreamManager

Use Guice AssistedInject to construct StreamManager
Refactor other components in log to be Guice-constructed.

More info: https://github.com/google/guice/wiki/AssistedInject

Testing Done:
./gradlew -Pq build

Also manually verified that the annotated methods are exported in
vagrant (by using aurora_admin scheduler_snapshot devcluster and
looking at /vars)

Reviewed at https://reviews.apache.org/r/25870/