Fix coverage testing for resolv_*_test

Bug: http://b/182009484

- Move resolv_unit_test to the tests/ subdir, so it can depend
  on libcrypto_static, which is visible to
  packages/modules/DnsResolver/tests but not
  packages/modules/Dnsresolver.
- Have resolve_gold_test depend on libcrypto_static.

If not, the tests depend on libcrypto.so for some LLVM coverage symbols,
causing failure when run on builds where libcrypto.so is not
instrumented for coverage.

Test: Verify coverage-enabled tests don't have any undefined __llvm_*
symbols.

Change-Id: I0fd9fdae9e55b7ad8159456518922c6a1ef4fc30