Finish moving to new APIs

src/core/ext/census/grpc_plugin.c

src/core/lib/support/string.c

test/core/bad_client/tests/large_metadata.c

test/core/channel/channel_args_test.c

test/core/channel/channel_stack_test.c

...client_channel/resolvers/dns_resolver_connectivity_test.c

test/core/client_channel/resolvers/dns_resolver_test.c

test/core/client_channel/resolvers/sockaddr_resolver_test.c

test/core/client_channel/set_initial_connect_string_test.c

test/core/compression/algorithm_test.c

test/core/compression/message_compress_test.c

test/core/end2end/bad_server_response_test.c

test/core/end2end/connection_refused_test.c

test/core/end2end/dualstack_socket_test.c

test/core/end2end/fixtures/h2_census.c

test/core/end2end/fixtures/h2_compress.c

test/core/end2end/fixtures/h2_load_reporting.c

test/core/end2end/fixtures/h2_oauth2.c

test/core/end2end/fixtures/h2_ssl.c

test/core/end2end/fixtures/h2_ssl_cert.c