WG21-P2757R3 Type-Checking Format Args
LWG-4142 format_parse_context::check_dynamic_spec should require at least one type

INCREASED feature-test macro, note special interactions with WG21-P2510R3 #3799 and WG21-P2637R3 #3808:

#define __cpp_lib_format 202305L // <== NOTE SPECIAL VALUE

Note: We're focused on implementing the remaining library-only features in C++23. Until that's done, we will NOT be accepting PRs for C++26 features.