Change types of fields of network stats reported to framework.

Currently, NetworkStats use int to handle uid, set and tag,
while native side using unsigned int mixing with signed int
with that. This commit make necessary changes in JNI part while
libnetdbpf unifying the types of fields.

Bug: 112226716
Bug: 119193941
Test: 1. manually reconnect vpn
      2. update apps from playstore
      3. atest libnetdbpf_test
      4. runtest frameworks-net
      5. cts-tradefed run cts -m CtsUsageStatsTestCases -t \
              android.app.usage.cts.NetworkUsageStatsTest

Change-Id: I6c27124db8292e2825fba51b8994f013897cb566
Merged-In: I6c27124db8292e2825fba51b8994f013897cb566
(cherry picked from commit bf7803eed8283d5a1caa2efe90aa449590ddb94f)
(cherry picked from commit f5bc6f61)