Add an experimental library to enable C++ compiler support for `union… #799

Job	Run time
ubu-24 \| g++-14 \| c++2b \| libstdc++ \| ubuntu-24.04	6m 3s
ubu-24 \| g++-13 \| c++2b \| libstdc++ \| ubuntu-24.04	5m 27s
ubu-20 \| g++-10 \| c++20 \| libstdc++ \| ubuntu-20.04	4m 52s
ubu-24 \| clang++-18 \| c++20 \| libstdc++ \| ubuntu-24.04	7m 6s
ubu-24 \| clang++-18 \| c++23 \| libc++-18-dev \| ubuntu-24.04	23s
ubu-22 \| clang++-15 \| c++20 \| libstdc++ \| ubuntu-22.04	5m 15s
ubu-22 \| clang++-15 \| c++20 \| libc++-15-dev \| ubuntu-22.04	5m 26s
ubu-20 \| clang++-12 \| c++20 \| libstdc++ \| ubuntu-20.04	4m 51s
mac-14 \| clang++ \| c++2b \| default \| macos-14	12s
mac-13 \| clang++ \| c++2b \| default \| macos-13	6m 32s
mac-13 \| clang++-15 \| c++2b \| default \| macos-13	8m 7s
win-22 \| cl.exe \| c++latest \| default \| windows-2022	4m 11s
win-22 \| cl.exe \| c++20 \| default \| windows-2022	4m 27s
aggregate-results	3s
	1h 2m 55s

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