Migrate IRegionSamplingListener interface to AIDL

This addresses security vulnerabilities due to hard coded binder
interface.

Bug: 195660647
Test: (1) atest RegionSamplingTest
      (2) install Google I/O 2019 app, tap Agenda menu, scrolling to
      examine the bottom horizontal bar color changes
Change-Id: I453e348461ff31b1e12a8080acb87e203dbe4ca0