Add ConnectivityAnnotations class

This change is to address API review, add respective
@IntDef for network policy API.

Typedef cannot be exposed as SystemApi so add
ConnectivityAnnotations class and add an annotation library
so that it can be used in module and platform.

Bug: 183972925
Test: m, build doc target framework-doc-stubs_annotations.zip
      and check the APIs have an attribute IntDef annotation
Change-Id: Ie3ec40cf48818edd422a4550377774eae387d3b2
diff --git a/service/Android.bp b/service/Android.bp
index 813a239..7265426 100644
--- a/service/Android.bp
+++ b/service/Android.bp
@@ -65,6 +65,7 @@
         "stable.core.platform.api.stubs",
         "android_system_server_stubs_current",
         "framework-annotations-lib",
+        "framework-connectivity-annotations",
         "framework-connectivity.impl",
         "framework-tethering.stubs.module_lib",
         "framework-wifi.stubs.module_lib",