Adding self-managed connection service APIs.

1. Adding new APIs for self-managed connection services.
2. Adding Telecom package-level documentation.

Test: Manual (unit, cts pending; this is just scaffolding for now)
Bug: 34159263
Change-Id: Ic226ec8bfcb2fbcc02fe802b47499e47aab17d0a

telecomm/java/android/telecom/RemoteConnectionService.java

@@ -367,6 +367,15 @@ final class RemoteConnectionService {
             }
         }
 
+        @Override
+        public void setAudioRoute(String callId, int audioRoute, Session.Info sessionInfo) {
+            if (hasConnection(callId)) {
+                // TODO(3pcalls): handle this for remote connections.
+                // Likely we don't want to do anything since it doesn't make sense for self-managed
+                // connections to go through a connection mgr.
+            }
+        }
+
         @Override
         public void onConnectionEvent(String callId, String event, Bundle extras,
                 Session.Info sessionInfo) {