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

framework/src/android/net/ConnectivityManager.java

@@ -40,6 +40,8 @@ import android.compat.annotation.UnsupportedAppUsage;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
+import android.net.ConnectivityAnnotations.MultipathPreference;
+import android.net.ConnectivityAnnotations.RestrictBackgroundStatus;
 import android.net.ConnectivityDiagnosticsManager.DataStallReport.DetectionMethod;
 import android.net.IpSecManager.UdpEncapsulationSocket;
 import android.net.SocketKeepalive.Callback;
@@ -4799,16 +4801,6 @@ public class ConnectivityManager {
             MULTIPATH_PREFERENCE_RELIABILITY |
             MULTIPATH_PREFERENCE_PERFORMANCE;
 
-    /** @hide */
-    @Retention(RetentionPolicy.SOURCE)
-    @IntDef(flag = true, value = {
-            MULTIPATH_PREFERENCE_HANDOVER,
-            MULTIPATH_PREFERENCE_RELIABILITY,
-            MULTIPATH_PREFERENCE_PERFORMANCE,
-    })
-    public @interface MultipathPreference {
-    }
-
     /**
      * Provides a hint to the calling application on whether it is desirable to use the
      * multinetwork APIs (e.g., {@link Network#openConnection}, {@link Network#bindSocket}, etc.)
@@ -5030,16 +5022,6 @@ public class ConnectivityManager {
     public static final String ACTION_RESTRICT_BACKGROUND_CHANGED =
             "android.net.conn.RESTRICT_BACKGROUND_CHANGED";
 
-    /** @hide */
-    @Retention(RetentionPolicy.SOURCE)
-    @IntDef(flag = false, value = {
-            RESTRICT_BACKGROUND_STATUS_DISABLED,
-            RESTRICT_BACKGROUND_STATUS_WHITELISTED,
-            RESTRICT_BACKGROUND_STATUS_ENABLED,
-    })
-    public @interface RestrictBackgroundStatus {
-    }
-
     /**
      * Determines if the calling application is subject to metered network restrictions while
      * running on background.