Summary:
Add new C APIs to create the JemallocNodumpAllocator and set it on a Cache object.

`make test` passes with and without `DISABLE_JEMALLOC=1`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8178

Reviewed By: jay-zhuang

Differential Revision: D27944631

Pulled By: ajkr

fbshipit-source-id: 2531729aa285a8985c58f22f093c4d53029c4a7b