Error/warning summary does not prioritize correctly

[mschubert]

When summarizing errors, they are currently ordered by comparing characters.

Error in summarize_result(re$result, length(re$errors), length(re$warnings),  :
  1/17183 jobs failed (5834 warnings). Stopping.
(#10) It appears as if you have specified a lower bounded prior on a pa
(#1000) It appears as if you have specified a lower bounded prior
(#10001) Examine the pairs() plot to diagnose
# actual error is not shown

Instead, they should be:

1. ordered by integer index
2. prioritizing errors over warnings