The symbols are inline and allocated together with the ConcurrentHashTable (CHT) Nodes. The calculation used for the required size is `alloc_size = size + value.byte_size() + value.effective_length();`

Where
  * `size == sizeof(SymbolTableHash::Node) == sizeof(void*) + sizeof(Symbol)`
  * `value.byte_size() == dynamic_sizeof(Symbol) == sizeof(Symbol) + <bytes beyond object>`
  * `value.effective_length() == dynamic_sizeof(Symbol) - sizeof(Symbol) == <bytes beyond object>`

So `alloc_size` ends up being `sizeof(void*) /* node metadata */ + 2 * dynamic_sizeof(Symbol)`