Clear counters and delete tag data from NetworkStatsService.

Currently, NetworkStatsService deletes tag data by calling
NetworkManagementSocketTagger, which then calls into libcutils
"qtaguid" code. Instead, make NetworkStatsService call into
libcutils directly and delete the NetworkManagementSocketTagger
code.

In the future, this will make it easier for NetworkStatsService
to perform this operation by calling directly into BpfNetMaps.

Because the unit test does not yet have working JNI code, provide
an internal TagStatsDeleter interface that can be mocked out via
the Dependencies class. This is a bit ugly but it will be deleted
as soon as the code uses BpfNetMaps directly.

Delete NetworkManagementSocketTagger#setKernelCounterSet since it
was replaced in aosp/1958917.

Also remove unused includes and make formatting changes suggested
by clang-format.

Test: m
Test: atest NetworkStatsServiceTest
Test: atest NetworkUsageStatsTest
Test: atest TrafficStatsTest
Test: stats deleted when CtsUsageStatsTestCases completes and test APK is uninstalled
Change-Id: I62987000afc185199821580232bfb7668c8e301e