Add the tests for ResolverStats

Add the test coverage for resolver stats. Also check and prune the
parameters in setResolverConfiguration() if they exceed the maximum
number predefined in params.h, and delete commented code.

Bug: 119694273
Test: system/netd/tests/runtests.sh passed

Change-Id: I265a2f03edd4fbc6df97270a782be5e639dfc5f8