Expose functions using zend_smart_str for PECLs calling simdjson_php bindings

[TysonAndre]

  /** ...
   * @param realloc_if_needed Whether to reallocate and enlarge the JSON buffer to add padding.
   * @return An element pointing at the root of the document, or an error:
   *         - MEMALLOC if realloc_if_needed is true or the parser does not have enough capacity,
   *           and memory allocation fails.
   *         - CAPACITY if the parser does not have enough capacity and len > max_capacity.
   *         - other json errors if parsing fails. You should not rely on these errors to always the same for the
   *           same document: they may vary under runtime dispatch (so they may vary depending on your system and hardware).
   */
  inline simdjson_result<element> parse(const uint8_t *buf, size_t len, bool realloc_if_needed = true) & noexcept;

If the capacity is at least 64 bytes larger than the string size, it's safe to avoid the extra copy and set realloc_if_needed=false, as long as the 64 bytes are initialized memory (any value) (not sure which architectures this matters for)