Refactor integration tests which using c-ares as DNS resolver

[yanjunxiang-google]

Title: Refactor integration tests which using c-ares as DNS resolver

Description: Right now there are a lot of integration tests are using c-ares DNS resolver. For example, some tests in below files:

1. test/integration/protocol/protocol_integration_test.cc
2. test/extensions/filter/http/dynamic_forward_proxy/proxy_filter_integration_test.cc 3)test/extensions/filters/network/sni_dynamic_forward_proxy/proxy_filter_integration_test.cc
3. test/extensions/filters/http/ext_authz/ext_authz_integration_test.cc ...

The idea is to

1. Replace c-ares DNS resolver with getAddrInfo DNS resolver in those tests.
2. Add several tests in test/extensions/network/dns_resolver/cares/dns_impl_integration_test.cc to cover c-ares integration tests.

[yanjunxiang-google]

/assign @yanavlasov