Include structs lib in service-connectivity-pre-jarjar

To use the java struct definitions for multicast routing in connectivity
service, a new lib is defined and included in
service-connectivity-pre-jarjar.

Bug: 323503345

Test: presubmit
Change-Id: I664602fd0fa0a5da136ea28fd3c4d9068c5b46ab
diff --git a/service/Android.bp b/service/Android.bp
index c6ecadd..89c83bd 100644
--- a/service/Android.bp
+++ b/service/Android.bp
@@ -197,6 +197,7 @@
         "PlatformProperties",
         "service-connectivity-protos",
         "service-connectivity-stats-protos",
+        "net-utils-multicast-forwarding-structs",
     ],
     apex_available: [
         "com.android.tethering",