treewide: Bump C++ standard version to C++23

Compilers in nixpkgs have caught up and major distros
should also have recent enough compilers. It would be
nice to have newer features like more full featured
ranges and deducing this.

src/libexpr-tests/derived-path.cc

@@ -1,5 +1,6 @@
 #include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
+#include <exception> // Needed by rapidcheck on Darwin
 #include <rapidcheck/gtest.h>
 
 #include "nix/store/tests/derived-path.hh"

src/libexpr-tests/meson.build

@@ -3,7 +3,7 @@ project(
   'cpp',
   version : files('.version'),
   default_options : [
-    'cpp_std=c++2a',
+    'cpp_std=c++23',
     # TODO(Qyriad): increase the warning level
     'warning_level=1',
     'errorlogs=true', # Please print logs for tests that fail