This patch changes the way of mocking samples in the tests, and
enabling use bpf stats flag, testing through the code path
that is not running in the production code does not make any
sense.
This change also copied methods from NetworkStatsFactory
as we want to continue parsing the golden files to test the
464xlat adjustment which historically has been prone to errors.
And deleting tests that does not execrise NetworkStatsFactory
code or rely on monotonic accumulative readings from native
layer, which is not happening today.
Bug: 234315786
Test: atest FrameworksNetTests CtsNetTestCases \
ConnectivityCoverageTests
Change-Id: I5cab2b78651f1da628705c191e42857c8b59d826
8c77e385bd