Provide a facility for thread-safe stdout/stderr redirection

[ngoldbaum]

See this comment in the CPython repo outlining a possible design for a context manager that sets up per-thread output redirection.

This could also live in a third-party project but I agree with Sam it probably makes sense to do here.

[15r10nk]

I would like to add that I have found another solution to my original problem, but I think the general case is still a problem.