Creates formatted string from format_args!()
like alloc::fmt::format()
but
without allocation:
rust
let mut buf = [0u8; 64];
let formatted: &str = stackfmt::fmt_truncate(&mut buf, format_args!("Hello{}", 42));
assert_eq!(formatted, "Hello42");
Implemented based on this SO answer https://stackoverflow.com/a/50201632/601298