At the moment if a test fails to hits the breakpoint we set in run_to_source_breakpoint
the test suite just prints:
AssertionError: 0 != 1 : Expected 1 thread to stop at breakpoint, 0 did
Often these errors happen because the debuggee crashed before that breakpoint is being
hit or the process failed to launch but it's hard to tell what happened from the current error.
This patch adds that we now print the backtrace of all threads in case the test failed
because we didn't hit the right breakpoint