Merge pull request #8049 from markdroth/grpclb_resolver_changes2

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/client_channel.h

src/core/ext/client_config/lb_policy_factory.c

src/core/ext/client_config/lb_policy_factory.h

src/core/ext/client_config/resolver_factory.h

src/core/ext/client_config/resolver_registry.c

src/core/ext/client_config/resolver_registry.h

src/core/ext/client_config/resolver_result.c

src/core/ext/client_config/resolver_result.h

src/core/ext/resolver/dns/native/dns_resolver.c

src/core/ext/resolver/sockaddr/sockaddr_resolver.c

...ore/ext/transport/chttp2/client/insecure/channel_create.c

...xt/transport/chttp2/client/secure/secure_channel_create.c

.../client_config/resolvers/dns_resolver_connectivity_test.c

test/core/client_config/resolvers/dns_resolver_test.c

test/core/client_config/resolvers/sockaddr_resolver_test.c