Create service-connectivity.jar

Create a new target service-connectivity to split
ConnectivityService from services.core.

Add ConnectivityServiceInitializer for initializing
ConnectivityService and add systemReady() in
ConnectivityManager so that SystemServer can call systemReady()
through ConnectivityManager which won't change current behavior.

Bug: 158268939
Test: make target-java, make host-java
      atest FrameworksNetIntegrationTests
      atest FrameworksNetTests
      make, device can boot,
      atest CtsStrictJavaPackagesTestCases
      wifi and mobile data work.
Change-Id: Ie732bfaf381404af0bb599ca2f421a96e7aa4257

core/java/android/net/ConnectivityManager.java

@@ -898,6 +898,18 @@ public class ConnectivityManager {
         }
     }
 
+    /**
+     * @hide
+     * TODO: Expose for SystemServer when becomes a module.
+     */
+    public void systemReady() {
+        try {
+            mService.systemReady();
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Checks if a given type uses the cellular data connection.
      * This should be replaced in the future by a network property.

core/java/android/net/IConnectivityManager.aidl

@@ -233,4 +233,6 @@ interface IConnectivityManager
 
     void simulateDataStall(int detectionMethod, long timestampMillis, in Network network,
                 in PersistableBundle extras);
+
+    void systemReady();
 }