Take non-incremental network stats from bpf maps

Use two maps to record the details of network stats. Swap and clean up
after system server pulls the stats. The TAG_STATS_MAP is removed since
we don't need to worry about losing the stats for each uid if the eBPF map
is full. All the stats can be stored in the same map now and it is very
unlikely to overflow the map before system server scrapes the stats and
clean it up. Add a benchmark test to measure the performance of creating
and closing pf_key socket. A typical result is:
------------------------------------------------------------------------
Benchmark                                 Time           CPU Iterations
------------------------------------------------------------------------
BpfBenchMark/WaitForRcu/1             86615 ns      54858 ns      20209

Bug: 79171384
Test: dumpsys netd trafficcontroller
      NetworkUsageStatsTest

Change-Id: Ic79e382f51bf21eee78c4cac5a8a97edaf3654cd