[DocDB] Remove GetAtomicFlag/SetAtomicFlag

[es1024]

Jira Link: DB-20204

Description

We currently have the GetAtomicFlag/SetAtomicFlag functions:

template <class T>
T GetAtomicFlag(T* flag) {
  std::atomic<T>& atomic_flag = *pointer_cast<std::atomic<T>*>(flag);
  return atomic_flag.load(std::memory_order::relaxed);
}

template <class U, class T>
void SetAtomicFlag(U value, T* flag) {
  std::atomic<T>& atomic_flag = *pointer_cast<std::atomic<T>*>(flag);
  atomic_flag.store(value);
}

which provide dubious value and are additionally also undefined behavior (there does not exist a std::atomic<T> object at the address pointed to by flag). These should be removed.

Issue Type

kind/bug

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