[NS08] Expose public NetworkScore API

This exposes the two bits settable by the network agents in
Android S on NetworkScore. This is meant to be extensible in
future releases, or possibly for OEM upstreams.

Test: builds
CTS-Coverage-Bug: 184037351
Bug: 167544279
Merged-In: I3c2563d4ae4e3715d0c6270344ba8f7ef067872f
Merged-In: Id7ee1bd3e2679f0bd5200d5c299f18a33b87847c
Change-Id: Id7ee1bd3e2679f0bd5200d5c299f18a33b87847c
  (cherry-picked from ag/14010221)

framework/src/android/net/NetworkScore.java

@@ -146,7 +146,7 @@ public final class NetworkScore implements Parcelable {
      *
      * @hide
      */
-    // TODO : @SystemApi
+    @SystemApi
     public boolean isTransportPrimary() {
         return hasPolicy(POLICY_TRANSPORT_PRIMARY);
     }
@@ -163,7 +163,7 @@ public final class NetworkScore implements Parcelable {
      *
      * @hide
      */
-    // TODO : @SystemApi
+    @SystemApi
     public boolean isExiting() {
         return hasPolicy(POLICY_EXITING);
     }
@@ -256,7 +256,7 @@ public final class NetworkScore implements Parcelable {
          * @return this builder
          * @hide
          */
-        // TODO : @SystemApi
+        @SystemApi
         @NonNull
         public Builder setTransportPrimary(final boolean val) {
             if (val) {
@@ -281,7 +281,7 @@ public final class NetworkScore implements Parcelable {
          * @return this builder
          * @hide
          */
-        // TODO : @SystemApi
+        @SystemApi
         @NonNull
         public Builder setExiting(final boolean val) {
             if (val) {