Move app uid stats map dump to NetworkStatsService

Map status dump will do access check if map is null.
This could show different message from the current dump output.

Information in map content dump does not change
$ dumpsys connectivity trafficcontroller
....
      mAppUidStatsMap::
      uid rxBytes rxPackets txBytes txPackets
      0 135 1 3602 47
      1001 2414 8 385 6
      1021 76 1 76 1
      1000 290 2 260 3
....
$ dumpsys netstats
....
  mAppUidStatsMap:
    uid rxBytes rxPackets txBytes txPackets
    0 135 1 3602 47
    1001 2414 8 385 6
    1021 76 1 76 1
    1000 290 2 260 3
....

Bug: 217624062
Test: dumpsys netstats, dumpstate, atest NetworkStatsServiceTest
Change-Id: I71988117c6dc3033f710b26a15d15879b35d50a4

tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java

@@ -2352,4 +2352,14 @@ public class NetworkStatsServiceTest extends NetworkStatsBaseTest {
         assertDumpContains(dump, "mUidCounterSetMap: OK");
         assertDumpContains(dump, "uid=1002 set=1");
     }
+
+    @Test
+    public void testAppUidStatsMap() throws ErrnoException {
+        initBpfMapsWithTagData(UID_BLUE);
+
+        final String dump = getDump();
+        assertDumpContains(dump, "mAppUidStatsMap: OK");
+        assertDumpContains(dump, "uid rxBytes rxPackets txBytes txPackets");
+        assertDumpContains(dump, "1002 10000 10 6000 6");
+    }
 }