BXL: get stdout/stderr of `actions.run()`

Is it possible to get the output of an action to print it out via `ctx.output.print()`?

The best I could do was redirect stdout to a declared output and print out its path, but since there is no way to read that file from BXL (that I know of anyway), this requires the user to `cat` out this file (potentially via a wrapper script), which is a poor UX.