BatteryService: implement HealthServiceWrapper

... which is a wrapper for @2.0::IHealth service that refreshes the
service if necessary. When new instances of IHealth are registered,
this class redirects its proxy to the new service.

Test: BatteryServiceTest
Bug: 63702641
Change-Id: I22f2aa1eb7d48a05dec5a7c747dabd6f832078e8