EMBMS - Add TestApi and provide service override

Add @TestApi annotations to methods that CTS needs
Add a manifest meta-data key that allows client apps to specify the
exact component name of the MBMS service to bind to.

Bug: 68049452
Test: CTS
Change-Id: I50654c41da38696a25fad93d0a5e0b0c11fa0b42
6 files changed