Dynamically stop lazy services

Services can choose to register with the new LazyServiceRegistrar.
ServiceManager perpetually checks the reference counts of services
registered in this way. If ServiceManager detects that a service no
longer has any clients, it will notify the LazyServiceRegistrar, which
will attempt to shut down the service.

Bug: 143108344
Test: aidl_lazy_test
Change-Id: Ic01981b767ab4402e7aecdf1cdf9ed64df1f5af4