Use structured logging

[SuperQ]

It would be nice to switch the logging from basic Go log to the new log/slog package. This would allow for both logfmt and json formatted logs. Having structured key=value logs is nicer to read than fmt.Sprintf() strings.

Also, it would be good to cleanup any use of fmt.Print(f|ln).

[SuperQ]

It seems like github.com/pion/logging is the current main logging library. It does not support structured logs.

[Nevexo]

It'd also be nice in the future to be able to stream logs to syslog etc.

[SuperQ]

I think syslog and related would be something we would need to file against the system distro (https://github.com/jetkvm/rv1106-system).