Add linkToDeath support for RPC binder so a client can act on disconnect

This requires an incoming thread to be listening to the connection in
order to be notified.

Test: atest binderRpcTest
Test: atest binderRpcTestSingleThreaded
Bug: 182939380
Change-Id: I3746de6e8cff99bb267867c5dc60a6815b19fb92
diff --git a/libs/binder/RpcState.h b/libs/binder/RpcState.h
index 892ecd6..7aab5ee 100644
--- a/libs/binder/RpcState.h
+++ b/libs/binder/RpcState.h
@@ -140,6 +140,11 @@
      */
     [[nodiscard]] status_t flushExcessBinderRefs(const sp<RpcSession>& session, uint64_t address,
                                                  const sp<IBinder>& binder);
+    /**
+     * Called when the RpcSession is shutdown.
+     * Send obituaries for each known remote binder with this session.
+     */
+    [[nodiscard]] status_t sendObituaries(const sp<RpcSession>& session);
 
     size_t countBinders();
     void dump();