Add RemoteAuthService APIs and Stubs (hide) for Settings of D2DA
This CL introduces new SystemApi allow user to discover remote devices
compatible to be registered as remote authenticators via RemoteAuthManager
Design doc: go/remote-auth-manager-fishfood-design
Test: built successfully.
Bug: 290092977
API-Coverage-Bug: 294934095
Change-Id: Iaaae1126065fdc3db469eeb8d85ac654b8199a12