Switch C++ standard to C++23 #612

Job	Run time
msvc-sanitisers (Release)	1m 40s
Valgrind	2m 2s
msvc-sanitisers (Debug)	1m 35s
build (macos-15, Debug, g++-14)	3m 44s
build (macos-15, Release, g++-14)	5m 6s
build (ubuntu-24.04, Release, clang++)	2m 50s
build (ubuntu-24.04, Release, g++-14)	2m 45s
build (windows-latest, Release, cl)	2m 42s
build (windows-latest, Debug, cl)	2m 53s
Coverage	2m 30s
clang-sanitisers (Debug)	46s
build (ubuntu-24.04, Debug, g++-14)	1m 36s
gcc-sanitisers (Debug)	1m 4s
build (ubuntu-24.04, Debug, clang++)	1m 37s
gcc-sanitisers (Release)	2m 52s
clang-sanitisers (Release)	2m 24s
clang-tidy	0s
	38m 6s

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