Add setPollForce to module API

The API was test API in S, but this is not supported in module API
surfaces. Make it module API instead.

Bug: 197717846
Test: Tests already using this API
  (cherry-picked from ag/16780943)
Change-Id: I9d44b761572f94b08b269478c4a0c20c1171343c
Merged-In: I9d44b761572f94b08b269478c4a0c20c1171343c

framework-t/src/android/app/usage/NetworkStatsManager.java

@@ -27,7 +27,6 @@ import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.SystemService;
-import android.annotation.TestApi;
 import android.annotation.WorkerThread;
 import android.app.usage.NetworkStats.Bucket;
 import android.compat.annotation.UnsupportedAppUsage;
@@ -192,9 +191,13 @@ public class NetworkStatsManager {
         }
     }
 
-    /** @hide */
+    /**
+     * Set poll force flag to indicate that calling any subsequent query method will force a stats
+     * poll.
+     * @hide
+     */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
-    @TestApi
+    @SystemApi(client = MODULE_LIBRARIES)
     public void setPollForce(boolean pollForce) {
         if (pollForce) {
             mFlags |= FLAG_POLL_FORCE;