Summary:
Optimize the management of available hazard pointers in the domain that are not in thread caches, by adding a linked list of available hazard pointers with a lock bit packed with the pointer to the head of the list. Pop operations are done in two atomic steps: (1) set lock bit, (2) pop hazard pointers and clear lock bit. Push operations are done in one atomic step, but can proceed only when the lock bit is clear.

Microbenchmark results (in a process with 10K+ hazard pointers) show reduction in the latency of constructing destroying two 9-hazard-pointer-arrays that involve one TC hit and one TC miss/overflow from hundreds of microseconds to tens of nanoseconds.

Before:
```
1/1000 TC hit + miss & overflow                   550 ns    502 ns    468 ns
```

After:
```
TC hit + miss & overflow                           49 ns     48 ns     48 ns
```

Reviewed By: yfeldblum

Differential Revision: D31102053

fbshipit-source-id: ae923bf3b05676e7572cca35179531e947846300