Implement metered tracking for NetworkStats summary queries.

Dependent on ag/1550196 where API is defined.

Bug: 31015360
Bug: 26545374
Test: runtest --path
frameworks/base/core/tests/coretests/src/android/net/NetworkStatsTest.java,
other test classes.

Change-Id: I968b9e3352d7880e3fc438f12de628a2da057e0a