Make test report and error buffers connection specific

[hugoduncan]

When working with multiple repls, the test report and error buffers are shared. This leads to

• the buffers often having the wrong directory associated with them
• test reports from one repl no longer linking to source properly whan a test i started in another repl
• test reports from one repl being lost when tests in another repl complete

Making these buffers connection specific would solve these issue.

[alexander-yakushev]

Thanks for bringing this up, Hugo! We certainly had a lot of problems with this earlier, and we still have some. However, I've tried to reproduce the issue you are describing (having two REPLs, running tests that fail in both of them, and trying to mix up the REPLs associated with each test buffer), and I couldn't achieve a behavior that would be incorrect. Would you be able to give reproduction steps that break it for you?