Avoid sorting and old results based on new query input string

RunnerResultsModel::setQueryString() was being called instantly as soon as we received a new input query string.
However at this moment it was still holding the matches set for the previous query, and not the matches for the new query string.
This caused it to re-sort the old set of matches based on the new string.
It was generating and displaying a bogus list to the user for a few moments.
Now we only forward the new query string to the RunnerResultsModel object after we receive a set of matches for the new query string, which fixes that problem.

CCBUG: 427672
2 jobs for !37 with avoid_proxying_old_output_based_on_new_input in 41 seconds (queued for 3 seconds)
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