Log transferring and fix verbose system logs

This CL logs transfer between routes to easily track potential bugs.
Selecting a route was also logged in MediaRouter.

It also reverts the log level of SystemMediaRoute2Provider because
we resolved issues related to it.

Bug: 156996903
Test: N/A
Change-Id: I6d7e165a79679305fd21a378fd3ae35b941c17c6