[Feature] Ability to select the output per reporter

I think it would be interesting to be able to choose the output per reporter, for example I would like to keep the console reporter on stdout but output the xml into a file.

The use case is for usage with CI, you usually want the console output in the logs, but still be able to interpret the output using a tool. Right now, if you use both reporters at the same time the output gets mixed.

From a command-line point of view, something like this could be used: --reporters=console:stdout,xml:results.xml