Use aligned allocation for hazptr_rec<Atom>

Summary:
The default allocator for `new` does not apparently respect the extended alignment requirement for `hasptr_rec<Atom>`. We use folly's AlignedSysAllocator for these cases, which will then pass UBSan checks for alignment.

```
xplat/folly/synchronization/HazptrDomain.h:572:20: runtime error: constructor call on misaligned address 0x60c0000004c0 for type 'hazptr_rec<atomic>', which requires 128 byte alignment
0x60c0000004c0: note: pointer points here
 02 00 00 7f  be be be be be be be be  be be be be be be be be  be be be be be be be be  be be be be
              ^
    #0 0x77949e in folly::hazptr_domain<std::atomic>::acquire_new_hprec() xplat/folly/synchronization/HazptrDomain.h:572:16
    #1 0x7791cc in folly::hazptr_domain<std::atomic>::hprec_acquire() xplat/folly/synchronization/HazptrDomain.h:227:35
    #2 0x766a7f in folly::hazptr_holder<std::atomic>::hazptr_holder(folly::hazptr_domain<std::atomic>&) xplat/folly/synchronization/HazptrHolder.h:71:21
    #3 0x766a7f in void folly::UnboundedQueue<folly::CPUThreadPoolExecutor::CPUTask, false, false, false, 6ul, 7ul, std::atomic>::enqueueImpl<folly::CPUThreadPoolExecutor::CPUTask>(folly::CPUThreadPoolExecutor::CPUTask&&) xplat/folly/concurrency/UnboundedQueue.h:374
```

Reviewed By: magedm

Differential Revision: D19237973

fbshipit-source-id: 0edea12bb3f028d21830689d52f7e0290d187ff9

folly/synchronization/HazptrDomain.h

@@ -21,6 +21,7 @@
 #include <folly/synchronization/HazptrRec.h>
 #include <folly/synchronization/HazptrThrLocal.h>
 
+#include <folly/Memory.h>
 #include <folly/Portability.h>
 #include <folly/executors/QueuedImmediateExecutor.h>
 #include <folly/synchronization/AsymmetricMemoryBarrier.h>
@@ -222,6 +223,10 @@ class hazptr_domain {
   }
 
  private:
+  using hazptr_rec_alloc = AlignedSysAllocator<
+      hazptr_rec<Atom>,
+      FixedAlign<alignof(hazptr_rec<Atom>)>>;
+
   friend void hazptr_domain_push_list<Atom>(
       hazptr_obj_list<Atom>&,
       hazptr_domain<Atom>&) noexcept;
@@ -463,7 +468,8 @@ class hazptr_domain {
     while (rec) {
       auto next = rec->next();
       DCHECK(!rec->active());
-      delete rec;
+      rec->~hazptr_rec<Atom>();
+      hazptr_rec_alloc{}.deallocate(rec, 1);
       rec = next;
     }
   }
@@ -597,7 +603,8 @@ class hazptr_domain {
   }
 
   hazptr_rec<Atom>* acquire_new_hprec() {
-    auto rec = new hazptr_rec<Atom>;
+    auto rec = hazptr_rec_alloc{}.allocate(1);
+    new (rec) hazptr_rec<Atom>();
     rec->set_active();
     rec->set_domain(this);
     while (true) {