Separate debugger stdout from debuggee stdout

[alt-romes]

With the advent of #44, we can send the debuggee output and receive input from a proxy running standalone in a terminal. This means on that terminal the debuggee input/output should be isolated from whatever messages the debugger has.

However, a few things leak from the debugger stdout because, well, things are printed to stdout/stderr rather than to the logger.

An example is the REPL mode, where you can input an expression like print 25. This goes to stdout by default.
I wonder if we can set up a redirection when we e.g. run a REPL command and restore the debuggee stdout when running the debuggee again. (like mask $ \restore -> ...)

Though I wonder how that would work if we support multiple threads running and only one is stopped while we're using the REPL...

[alt-romes]

I wonder if this could be achieved by using the external interpreter somehow exclusively for the debuggee