Function make_json_numeric_sort_key

Make a sort key for a JSON numeric value from its string representation. The input string could be either on scientific format (such as 1.234e2) or on plain format (such as 12.34). The sort key will have the following parts: 1) One byte that is JSON_KEY_NUMBER_NEG, JSON_KEY_NUMBER_ZERO or JSON_KEY_NUMBER_POS if the number is positive, zero or negative, respectively. 2) Two bytes t