- Performance improvements
- Added `span` for zero-copy pointer+length arguments
- Added `std::ostream` overload for direct writing to output buffers
- Removal of unused `string_tools::buff_to_hex`
The default behavior for hex string parsing would allow the
last digit to be made from a single hexadecimal character,
which is correct, but we typically do not want that as it
gets confusing and easy to not spot wrong input size.
