refactor(io): move meta traits from core

Author: GaspardKirira

CMakeLists.txt

@@ -323,6 +323,7 @@ message(STATUS "Tests:              ${VIX_IO_BUILD_TESTS}")
 message(STATUS "Include dir:        ${CMAKE_CURRENT_SOURCE_DIR}/include")
 message(STATUS "Public headers:")
 message(STATUS "  - <vix/io/...>")
+message(STATUS "  - <vix/meta/...>")
 message(STATUS "  - <vix/print.hpp>")
 message(STATUS "  - <vix/format.hpp>")
 message(STATUS "  - <vix/inspect.hpp>")