CI:Test time limit with thread dump report

In another attempt to debug log writing failed. closed stream, I'm adding a test deadline monitor thread to our CI test runs. This specific run ran for 5 hours 😮

This monitor will dump the stack track of all threads after 30 minutes and kill the RSpec process with a non-zero exit code.

None of our tests are close to taking 30 minutes (the slowest tests, for JRuby, take around 6 minutes).

Hopefully this will allow debugging not only this specific issue, but any other tests that happen to get stuck in the future.