Summary:
- Add support for private lists of retired objects
- Add an option for one domain
- More scalable thread cache managemnt
- hazptr_rec alignment
- FOLLY_ALWAYS_INLINE
- Refactor management of retired objects in hazptr_domain
- Refactor benchmarks

Reviewed By: davidtgoldblatt

Differential Revision: D5322646

fbshipit-source-id: 9d31582b9a8216861e7e78e2e1cd08dc11cf7f88