Use session hints when create a session from MR2Manager

When MR2Manager requests to create a routing session, it should pass
session hints to the target provider.
This CL adds a logic that MR2Manager asks media router instance to
get session hints to be passed to the provider.

Bug: 152851868
Test: atest mediaroutertest
Change-Id: Ib421f61f663090c6ed95c8b1a2f7deeb80e5be16
6 files changed