Add support for move operations on hazptr-holder. Other optimizations.

Add support for move operations on hazptr-holder. Other optimizations.

Summary:
- Support empty hazptr_holder, move constructor and assignment operator
- Limit thread caching to the default domain to improve performance of thread caching
- Fix unnecessary calls to stats singleton
- Use the mprotect version of AsymmetricMemoryBarrier for reducing the overhead of bulkReclaim().
- Update read-side benchmark results

Reviewed By: djwatson

Differential Revision: D5292885

fbshipit-source-id: bc5713ac95492a7114e1e467e71d2278e64b165d