Add multipath preference, background status API

Add APIs for getMultipathPreference and getRestrictBackgroundStatus.
Both are used by Connectivity to back the external
ConnectivityManager.getRestrictBackgroundStatus, and
ConnectivityManager.getMultipathPreference APIs.

Test: atest CtsNetTestCases
      atest ConnectivityServiceTests
      atest NetworkPolicyManagerServiceTest
Bug: 176289731
Change-Id: I8a03162b2f6691086bb64e75ffd354cdfca7f86a
Merged-In: I8a03162b2f6691086bb64e75ffd354cdfca7f86a
diff --git a/framework/src/android/net/IConnectivityManager.aidl b/framework/src/android/net/IConnectivityManager.aidl
index d83cc16..98f3d40 100644
--- a/framework/src/android/net/IConnectivityManager.aidl
+++ b/framework/src/android/net/IConnectivityManager.aidl
@@ -220,4 +220,6 @@
 
     void setProfileNetworkPreference(in UserHandle profile, int preference,
             in IOnCompleteListener listener);
+
+    int getRestrictBackgroundStatusByCaller();
 }