- move utf8 stream and format patch from string to patch namespace.
- add ordinay format alias and utf8 format in our format patch.
- add char8_t and char inter-cast in string reinterpret namespace.
- fix bug of utf8 formatter.
- add test for utf8 format.
- add compiler hint for checking the arguments of printf.
- change the return value of printf. from std::expected to normal value. use C++ exception to indicate error.
* the error of printf usually caused by programmer. so it can be found when testing program.
* so i use std::logic_error to indicate this and programmer should fix this before releasing program.
- change the use of encoding convertion. for those cases that convertion must be safe, we unwrap it directly.
