Add LinkProperties methods to system APIs

The exposed methods are used by telephony, wifi
and tethering. For mainline support, making the
methods @SystemApi.

Bug: 139268426
Bug: 135998869
Bug: 138306002
Test: atest FrameworksNetTests
      atest NetworkStackTests
      atest FrameworksTelephonyTests
      ./frameworks/opt/net/wifi/tests/wifitests/runtests.sh
      atest android.net.cts
      atest android.net.wifi.cts
      atest android.telephony.cts

Change-Id: Ib16a838cf9f748e1c5b045d6c2f17678f16af28c
diff --git a/core/java/android/net/LinkProperties.java b/core/java/android/net/LinkProperties.java
index 8e18341..f8ded62 100644
--- a/core/java/android/net/LinkProperties.java
+++ b/core/java/android/net/LinkProperties.java
@@ -227,7 +227,7 @@
     /**
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public @NonNull List<String> getAllInterfaceNames() {
         List<String> interfaceNames = new ArrayList<>(mStackedLinks.size() + 1);
         if (mIfaceName != null) interfaceNames.add(mIfaceName);
@@ -247,7 +247,7 @@
      * @return An unmodifiable {@link List} of {@link InetAddress} for this link.
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public @NonNull List<InetAddress> getAddresses() {
         final List<InetAddress> addresses = new ArrayList<>();
         for (LinkAddress linkAddress : mLinkAddresses) {
@@ -342,8 +342,8 @@
      * Returns all the addresses on this link and all the links stacked above it.
      * @hide
      */
-    @UnsupportedAppUsage
-    public List<LinkAddress> getAllLinkAddresses() {
+    @SystemApi
+    public @NonNull List<LinkAddress> getAllLinkAddresses() {
         List<LinkAddress> addresses = new ArrayList<>(mLinkAddresses);
         for (LinkProperties stacked: mStackedLinks.values()) {
             addresses.addAll(stacked.getAllLinkAddresses());
@@ -542,6 +542,7 @@
      * @return true if the PCSCF server was added, false otherwise.
      * @hide
      */
+    @SystemApi
     public boolean addPcscfServer(@NonNull InetAddress pcscfServer) {
         if (pcscfServer != null && !mPcscfs.contains(pcscfServer)) {
             mPcscfs.add(pcscfServer);
@@ -729,7 +730,7 @@
      * Returns all the routes on this link and all the links stacked above it.
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public @NonNull List<RouteInfo> getAllRoutes() {
         List<RouteInfo> routes = new ArrayList<>(mRoutes);
         for (LinkProperties stacked: mStackedLinks.values()) {
@@ -1025,7 +1026,7 @@
      * @return {@code true} if there is an IPv4 default route, {@code false} otherwise.
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public boolean hasIpv4DefaultRoute() {
         for (RouteInfo r : mRoutes) {
             if (r.isIPv4Default()) {
@@ -1082,7 +1083,7 @@
      * @return {@code true} if there is an IPv4 DNS server, {@code false} otherwise.
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public boolean hasIpv4DnsServer() {
         for (InetAddress ia : mDnses) {
             if (ia instanceof Inet4Address) {
@@ -1110,7 +1111,7 @@
      * @return {@code true} if there is an IPv6 DNS server, {@code false} otherwise.
      * @hide
      */
-    @UnsupportedAppUsage
+    @SystemApi
     public boolean hasIpv6DnsServer() {
         for (InetAddress ia : mDnses) {
             if (ia instanceof Inet6Address) {