Refactoring of deleting stats in NetworkStats based on uids.

In follow-up commits, current API would create new NetworkStats
every time when 464xlatAdjustment wants to filtered out some
uids.

This commit refactors it to delete stats in-place to get better
performance.

Bug: 118602783
Test: atest FrameworksNetTests
Change-Id: I858f95d1fa7733111786243b4e261ce8a70a068d
diff --git a/services/core/java/com/android/server/net/NetworkStatsRecorder.java b/services/core/java/com/android/server/net/NetworkStatsRecorder.java
index a16dcf3..a2e7e0c 100644
--- a/services/core/java/com/android/server/net/NetworkStatsRecorder.java
+++ b/services/core/java/com/android/server/net/NetworkStatsRecorder.java
@@ -352,7 +352,7 @@
 
         // Clear UID from current stats snapshot
         if (mLastSnapshot != null) {
-            mLastSnapshot = mLastSnapshot.withoutUids(uids);
+            mLastSnapshot.removeUids(uids);
         }
 
         final NetworkStatsCollection complete = mComplete != null ? mComplete.get() : null;