Separate Struct.java into its own lib.

* Struct.java is removed from net-utils-device-common-bpf and
  net-utils-device-common-struct's source list
* Created a lib net-utils-device-common-struct-base for Struct.java
* Updated libs that require Struct.java to include
  net-utils-device-common-struct-base.
* Replaced net-utils-multicast-forwarding-structs with
  net-utils-device-common-struct in service-connectivity

Bug: 323503345

Test: build tethering module.
Change-Id: I3f60715c3d8043b7569db7612dee9d4fa1ccba59
diff --git a/service/Android.bp b/service/Android.bp
index c35c4f8..1d74efc 100644
--- a/service/Android.bp
+++ b/service/Android.bp
@@ -199,7 +199,9 @@
         "PlatformProperties",
         "service-connectivity-protos",
         "service-connectivity-stats-protos",
-        "net-utils-multicast-forwarding-structs",
+        // The required dependency net-utils-device-common-struct-base is in the classpath via
+        // framework-connectivity
+        "net-utils-device-common-struct",
     ],
     apex_available: [
         "com.android.tethering",