Move NetworkStatsFactory into service directory

In order to notify netd to swap eBPF maps before pulling the
networkStats from eBPF maps, NetworkStatsFactory need to use the
NetdServices to issue binder calls. So it need to be moved from
framework/base/core to framework/base/service since object in
framework/base/core cannot get any system services. This change is also
necessary for setting up a lock inside NetworkStatsFactory to prevent
racing between two netstats caller since the lock need to be hold before
netd trigger the map swap.

Also fix the compile problem caused by moving the NetworkStatsFactory
and the related tests. Rename the packages and the jni functions to a
more proper name.

Bug: 124764595
Bug: 128900919
Test: NetworkStatsFactoryTest
      android.app.usage.cts.NetworkUsageStatsTest
      android.net.cts.TrafficStatsTest

Change-Id: Ifcfe4df81caf8ede2e4e66a76552cb3200378fa8