[CMake][NewPM] Move ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER into llvm/ This allows us to use its value everywhere, rather than just clang. Some other places, like opt and lld, will use its value soon. The #define for it is now in llvm-config.h. Reviewed By: rnk, hans Differential Revision: https://reviews.llvm.org/D92072 GitOrigin-RevId: a36bd4c90dcca82be9b64f65dbd22e921b6485ef