Support stdio flush runtime option

[edubart]

Context

When running heavy console applications in non interactive mode (e.g a heavy LLM which can take hours to process) the stdout is flushed only on every new line, meaning it's impossible to see intermediary sentence output tokens being generated lively, ideally we want let users hacking to see what is being generated in the console.

Possible solutions

We could add new runtime option to set stdout flushing scheme (e,g every new line, every character, or never flush).