Add `GetEnumConstantDatamembers` function #341

Job	Run time
osx15-arm-clang-clang-repl-19	8s
osx15-arm-clang-clang-repl-18	8s
osx15-arm-clang-clang-repl-17	8s
osx15-arm-clang-clang-repl-16	9s
osx15-arm-clang-clang13-cling	9s
osx15-arm-clang-clang-repl-19-cppyy	4m 45s
osx15-arm-clang-clang-repl-18-cppyy	4m 47s
osx15-arm-clang-clang-repl-17-cppyy	4m 33s
osx15-arm-clang-clang-repl-16	4m 6s
osx15-arm-clang-clang13-cling-cppyy	4m 43s
	23m 36s

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