cmake AGRPC_TEST_HAS_STD_PMR examples

Tradias/asio-grpc test/utils/CMakeLists.txt :128

target_compile_definitions(
        ${_asio_grpc_name} PUBLIC "ASIO_GRPC_TEST_CPP_VERSION=\"${_test_suite_name} C++${_asio_grpc_cxx_standard}\""
                                  $<$<BOOL:${ASIO_GRPC_HAS_STD_PMR}>:AGRPC_TEST_HAS_STD_PMR>)