Support reflection on namespaces, including the parent namespace #896

Job	Run time
ubu-24 \| clang++-19 \| c++23 \| libc++-18-dev \| ubuntu-24.04	8m 4s
ubu-24 \| g++-14 \| c++2b \| libstdc++ \| ubuntu-24.04	7m 2s
ubu-22 \| clang++-15 \| c++20 \| libstdc++ \| ubuntu-22.04	5m 43s
ubu-24 \| g++-13 \| c++2b \| libstdc++ \| ubuntu-24.04	6m 46s
ubu-24 \| clang++-19 \| c++20 \| libstdc++ \| ubuntu-24.04	8m 11s
mac-14 \| clang++ \| c++2b \| default \| macos-14	2m 29s
mac-13 \| clang++ \| c++2b \| default \| macos-13	5m 51s
win-22 \| cl.exe \| c++latest \| default \| windows-2022	32s
win-22 \| cl.exe \| c++20 \| default \| windows-2022	25s
mac-13 \| clang++-15 \| c++2b \| default \| macos-13	10m 9s
ubu-22 \| clang++-15 \| c++20 \| libc++-15-dev \| ubuntu-22.04	6m 9s
aggregate-results	3s
	1h 1m 24s

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