In ordinary times, the question motivating the 12 short plays in TheatreFirst’s “Participants” might not sound like a theme around which you could organize a single evening of theater: “Where have we been, what are we doing, and where do we go now?” In other words: write a short play about anything that has ever existed or might yet exist? But the company posed the question to its playwrights, all of whom are local or have strong local ties, specifically in the wake of the 2016 presidential election — i.e., in extraordinary times.