Method do_allocate

test/reusable/test_memory_resource.cpp:27–30

struct MockResource : public ::std::pmr::memory_resource {
  virtual void* do_allocate(size_t bytes, size_t alignment) noexcept override {
    allocate_called = true;
    return ::operator new(bytes, ::std::align_val_t(alignment));
  }

  virtual void do_deallocate(void* ptr, size_t bytes,
                             size_t alignment) noexcept override {