Add an API hint for metered multipath traffic.

This allows an application that knows how to provide seamless
network connectivity (e.g., using QUIC multipath) to find out if
doing so is desired.

(cherry picked from commit 2de4925f5cc64aeb92e02a8f740d3ff20f36dddd)

Test: builds, boots, runtest frameworks-net passes.
Bug: 34630278
Change-Id: Ic7fd0b9e1cd879fdfaf84009d7125391895e9087
diff --git a/core/java/android/net/IConnectivityManager.aidl b/core/java/android/net/IConnectivityManager.aidl
index b123c28..425e494 100644
--- a/core/java/android/net/IConnectivityManager.aidl
+++ b/core/java/android/net/IConnectivityManager.aidl
@@ -161,6 +161,8 @@
     void setAcceptUnvalidated(in Network network, boolean accept, boolean always);
     void setAvoidUnvalidated(in Network network);
 
+    int getMultipathPreference(in Network Network);
+
     int getRestoreDefaultNetworkDelay(int networkType);
 
     boolean addVpnAddress(String address, int prefixLength);