to_string() vs to_owned #

• to_string use formatting framework in the past, but it’s specialized now. So use it now!
• to_owned simpler internal allocation

1. https://users.rust-lang.org/t/to-string-vs-to-owned-for-string-literals/1441/3
2. https://medium.com/@ericdreichert/converting-str-to-string-vs-to-owned-with-two-benchmarks-a66fd5a081ce#:~:text=to_string()%20is%20the%20generic,the%20literal%20into%20the%20buffer.
3. https://www.youtube.com/watch?v=3iC3FVS6UXQ