Fix RcsManager and add empty RcsThread class

This change fixes the RcsManager setup and adds an empty RcsThread class. Please see go/rcs-in-telephony-doc for details.

Test: Builds fine
Bug: 109759350
Merged-in: Ie3fe476ab11d515ffab6dcc6ccf5ec801a4c9057
Change-Id: Ie3fe476ab11d515ffab6dcc6ccf5ec801a4c9057
10 files changed