Summary: Reuse WITH_JEMALLOC option in preparation for module search unification. Move jemalloc overrides into a separate .cc Remote obsolete JEMALLOC_NOINIT option. Closes https://github.com/facebook/rocksdb/pull/3078 Differential Revision: D6174826 Pulled By: yiwu-arbug fbshipit-source-id: 9970a0289b4490272d15853920d9d7531af91140